Tryteyker-
This function goes through config values and as such is dependant on these. In some instances, this can lead to weird results; the user may, for example, expect the skids on the Littlebird to be cargo slots.
However, in reality, they are not and as such will be counted even if the boolean value is set to false.
If the bool value is set to true, it will return the total amount of seats available. To get the cargo seats only, running this function twice (once with false and once with true as bool values), and then subtracting the total with crew-only will yield the cargo (F^cargo = Ftotal - Fcrew) slots.
Crew slots include gunners and in some instances some cargo slots. The above may not work for every vehicle.