When drilling down on an "MC" source journal, it brings up Payment History Inquiry instead of AP Invoice History?

Hello all,

I am looking in Account Inquiry at AP and MC source journal entries.  Drilling down on AP entries brings up AP Invoice History information.  However, drilling down on an MC entry brings up only Payment History Inquiry.   Does anyone know why?   What is our AP person doing in order to create the MC source journal entries?

I suspect that it may be that our AP person is entering a payment and then creating the invoice on the fly?   Or is created by doing something else?

Thanks.