If the participants are given equal shares/sign-ups in your co-op:

Participant No. 1 (the first affiliate on your list of participants) gets the first sign-up.
Participant No. 2 gets the second sign-up.
Participant No. 3 gets the third sign-up, and so on.

Once it reaches the end of your list, the rotation starts over at the top and repeats this process for as long as sign-ups keep coming in.

If differing numbers of lead/share values are given to participants, the system will distribute the sign-ups proportionally. For example: If Participant No. 1 is to be given 2 sign-ups, and Participant No. 2 is marked down to receive 5 sign-ups...The first lead will go to Participant No. 1. The next three sign-ups will go to Participant No. 2. The fourth lead will go to Participant No. 1. The remaining two sign-ups will then go to Participant No. 2.