I would guess that the A and B set have different reporting numbers, this seems logical.
I think whether a 3 or a 5 car unit,the unit has the same road # as the cars are treated as 1 unit. The next 3-5 car unit is another car number. If they're 1 single car with a knuckle coupler on each end of 1 single car,then each single car carries a separate car number. However when you have 3 or 5 cars,with a knuckle on each end of that 3 or 5 car unit,then those cars are regarded as 1 unit with the same reporting number.
Al Hummel