4000 divided by 4 gives 1000 passengers on-board. How the hell you made 500 out of it?
Edit:
The problem is mainly caused by freighters, because there's no way that freighter would take more than 100-200 people - all in comparison to the pilot's model.
Original Humpback could take up to 250 commodities, but then it was a pretty bulky and rather big freigher.
