It can't, but it always attempts to. For example, let's say you've chosen a SHARES type co-op. You've got 10 participants and your advertising generates 99 sign-ups total. It would rotate through all 10 participants as the sign-ups come in. The first nine participants would get 10 sign-ups each and the 10th participant would wind up with nine sign-ups. It's first come, first serve, but if the right number of sign-ups is generated (100 for the above example), the system will indeed give each participant EXACTLY the same amount of sign-ups each.