Hi, on your OFP, it has the following dispatch remark:
PAYLOAD/CARGO LIMITED BY MLW
In order to not exceed the aircraft’s max landing weight at destination, it isn’t possible to take on 170 passengers weighing 230 lbs each (assuming 175 for the passenger and 55 for their bags, as SimBrief normally does). SimBrief won’t offload the extra 30 minutes of fuel you requested, since it is assumed that you had a good reason to need it, so it has to offload payload instead to make the numbers fit.
It seems like FlyByWire is simply loading the passenger count from SimBrief, multiplying it by 230, and adding that to the OEW. But in cases where the payload is arbitrarily limited by the MLW/MZFW/MTOW, this will create discrepancies as you have seen.
For this reason, the recommended way for FlyByWire to program their SimBrief import would be to directly import the ZFW number itself (rather than the passenger count number). If their load editor doesn’t support entering the ZFW directly, they might need to do some math in the back-end to calculate exactly how many passengers should be entered to result in the desired ZFW. Unless there is an “average passenger weight” that they can adjust instead.