The display charge indicator has a lagging system so that it’ll stabilize in cases of voltage fluctuations.
Switch the bike ON
Ride for 10-15 sec, and the bars will show full.
At no load condition ~42V is fully charged ~32V is fully discharged. You can estimate the charge level almost linearly in between. For example, 37V is half way. The best way to see the accurate charge level of the battery is to page the screen by clicking the power button twice. The battery Voltage will show up at the bottom of the screen.