Radiocarbon dating 

Most writings on the DSS say they are mostly dated between 150 BCE and 70 CE. I see the section on radiocarbon dating here mostly falls in that general line (that is also used at the start of this article). I see that one radiocarbon dating cited here says they fall between 385 BCE to 82 CE with "68%" reliability (not sure of the correct term used for this part of the dating). Does anyone know a lot about these dating methods? I'm guessing since the 150 BCE to 70 CE is the usual range always given, the 385 BCE is an outlier (as I've never heard any number going back beyond 200 BCE in anything I've read) not sure how this relates to the 68% number provided on that as well. Just wondered if anyone had any background info on that as it can be seen as contradictory (with the usual 150 BCE- 70 CE dating given everywhere else).