Date: 202010
Local time of day: 0601-1200
Location: ZZZ.Airport, US
Aircraft: Commercial Fixed Wing
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Parked
Reporter organization: Air Carrier
Reporter function: Pilot Flying; Captain
Reporter qualification: Flight Crew Instrument; Flight Crew Multiengine; Flight Crew Air Transport Pilot (ATP)
Human factors: Distraction; Training / Qualification; Communication Breakdown; Confusion
Anomaly: Deviation / Discrepancy - Procedural Published Material / Policy; Deviation / Discrepancy - Procedural Weight And Balance
Detector: Person Flight Crew
When detected: Aircraft In Service At Gate
Contributing factors: Human Factors; Company Policy
Primary problem: Human Factors

Narrative: During boarding; two jumpseaters came up to the cockpit to identify themselves and ask permission to ride. The first one was originally assigned the jumpseat; but was told by the gate agent to take [seat] X1; and his coworker was assigned X2. Prior to departure; we became aware of a cargo loading issue that required both my and the FO's attention; and we both diverted most of our focus to taking care of that and getting the manifest to match where the cargo was moved. During this time; the gate agent sent the passenger numbers via auto-closeout. They indicated that there was an additional crew member listed (totaling X crew); and Y passengers in Zone X (where row X is located). I was aware that we needed to remove the additional crew member from the crew total and move him to Zone X; where [he] was actually seated; but it was my understanding that the Zone X total did not include the second jumpseater who was also assigned row X; as a result; we added two passengers to the Zone X total; making it [a count of] Z.After this occurred; ramp re-sent our cargo numbers; and somehow in that process our passenger numbers were reset to their original; too. After this occurred; we again removed the additional crew member from the crew total and changed Zone X back to Z instead of X passengers. At this point; I asked the Flight Attendant to count the number of passengers in Zone X; just to make sure it correlated with the change we made in the ACARS. She confirmed that there were Z passengers seated in Zone X. We sent for the manifest with that load and departed for a normal flight. During our next flight; we were faced with an almost identical situation with two jumpseaters. In discussion with this gate agent; he made it clear to us that when they send the passenger count via auto-closeout; the second jumpseater is already included in the passenger count; meaning we only need to remove the additional crew member from the crew total and put them in their respective zone if they are also assigned a seat in the back. Based on this information; I then realized that on our previous flight the passenger total already included one of the jumpseaters; and by adding 2 to Zone X; we ended up sending the manifest with an incorrect passenger total; in the sense that we added in one more than there actually was. As a result; our calculated versus actual weight was off by the weight of one adult passenger. We experienced confirmation bias in me asking the Flight Attendant to count Zone X; due to the fact that we heard what we expected to hear; but likely a totally unrelated passenger had moved into Zone X without their noticing; which resulted in her telling us we had Z in Zone X.This event was caused largely by not understanding some of the smaller details of the auto-closeout process. I do not recall personally having a situation before where we have had two jumpseaters on a not-full aircraft. It was my understanding that a jumpseater assigned a cabin seat needed to be manually placed there and wouldn't be included in the auto-closeout sent by the gate agent; the exception being if they are included in the auto-closeout crew total as an additional crew member in the actual jumpseat; but need to be moved to the correct zone if assigned a cabin seat prior to departure. That logic was incorrect; as confirmed when the next flight's gate agent mentioned that the first jumpseater is always listed as an additional crew member in the actual for auto-closeout; and any subsequent jumpseater is scanned on as any passenger would be; which would include them in the auto-closeout total. Also contributing to this was the distraction with the ramp agents and making sure that our cargo was loaded correctly. That task saturation combined with nearing departure time led to distraction and a bit of rushing that kept me from slowing down and thinking carefully about the jumpseater seating situation. Additionally; our flight attendants informed us that on this particular partner; paper sheets were no longer available; and so conducting a full passenger count didn't necessarily come to mind. Having asked them to do one likely would have us discovering that our ACARS manifest total did not match their passenger count.In the future; especially with COVID seating restrictions that complicate accommodating jumpseaters; I will be extremely vigilant in these situations to confirm with the gate agent that if there are multiple jumpseaters; that they are accounted for in the auto-closeout already. Doing so will prevent these double counting errors and ensure greater accuracy. If there is ever any question; I'll not be shy to ask the flight attendants to conduct a passenger count to ensure the greatest and most up to date information. Finally; to prevent rushing associated with task saturation; I'll be very diligent about taking things deliberately slowly and only accomplishing one task at a time; to prevent errors like this from occurring. From a technical standpoint; it could also be helpful to include the number of jumpseaters on board in the remarks section of the auto-closeout. 'Additional crew member Listed' seems to have the connotation of only one being on board; and could potentially be misinterpreted.




Synopsis: Air carrier Captain reported a weight and balance issue due to a misunderstanding of the passenger counting process.