Every flight is loaded piece by piece — no flat estimates. Behind the flight number sit named passengers with cabin class and special requests, their physical baggage and real belly freight (consignments with an air waybill).
From that the system computes a full loadsheet: DOW → ZFW → TOW, checked against the structural limits MZFW, MTOW and MLW. You carry that zero-fuel weight into your SimBrief OFP — your Fenix, FlyByWire or Inibuilds loads the exact same number in the sim. The crew briefing also shows the pax, baggage and cargo manifest.