sd or daris might be able to better advise, but i'd think you'd want to get an aadvantage# first if you don't already have one. then you enter that in your cc applications. if you don't have a number to enter i'd guess you'd get a diff. # assigned to you for each card, assuming you apply for both at the same time.
it probably wouldn't be that hard to fix if they gave you two numbers though.