Where do you define (or can you) what a "Sign Up" is in Affiliates Plugin (with marketpres

I am using the affiliates plugin with markeptress and paypal payflo pro over at 60daymba.com

I have our affiliate program properly tracking unique clicks - but I don't know what a "sign up," is.

If it considers a signup to be a new blog registrant (IE http://60daymba.com/wp-login.php?action=register) then I think that will never happen (we only sell classes we do not have blog members).

However - we do take mailchimp email signups and that would be OUR second step in teh funnel - it would be nice to define that as a "sign up." Is that possible? Or am I stuck with only unique clicks and purchases?