Depends on TG definitions (TwoWay or OneWay TG), How Many circuits do you have in these TG. If this Switch is 100% gateway then the incoming traffic must be equal to the outgoing traffic then the name of the TG is different but the circuits are the same. Finally the total traffic is the number of erlang of one of the TG defined.
I think that you have the same capacity on both TG (in & out).