how it really works?

hi there,
i have the affiliates plugin installed on my multisite, but after going through the documentation, i still don't understand how it works.
i have a multisite with pro-sites plugin installed. i have user creating websites and paying for it monthly, every 3months or every 12months. so, if one of my multisite users will enable affiliate links and then someone will go to my website, sign up and start paying monthly, what's that person getting for referring a new paying user? would that be a percentage from that monthly fee? how long for would that last for?
it's a bit unclear from the documentation so i'd really appreciate clarifying that for me.
thanks,
Adam