I suppose that is in this xml section ?
<!-- A318 -->
(L:AB_TypeIdent, number) 12 ==
132 (>L:MCDU2_FP_max_Pax, number)
17.00 (>L:MCDU2_FP_max_Cargo, number)
19.15 (>L:MCDU2_FP_max_Fuel, number)
68.00 (>L:MCDU2_FP_max_Tow, number)
39.51 (>L:MCDU2_FP_empty_weight, number)
I have the same value for "max_cargo" ans "max_fuel" for A318/319/320/321MCDU2c.xml. It's strange... if the plane is bigger, the more fuel and cargo it can carry...
NB : After vérification, this issue is only for A318