FraPre wrote on Dec 23^rd, 2018 at 4:29pm:

Sorry, the answer with the 40/300 passengers and 100/100 freight can not be meant seriously! Maybe I have read it over, but it is sad that this information about the underlying configuration is not in the manual. This is important for the correct configuration of planning tools.

They are the MAXIMUM numbers you can enter in each section (Business, Coach, Cargo Fwd, and Cargo Aft), I never use those maximum numbers at the same time, simply because they would make the 757 too heavy! In fact I have never used the maximum at any other time, other than when I determined what they were, and I never did a flight (I don't think it would have taken off) with them either.  ;D