I joined Date.com and I am curious how they track affiliate sales?

When I login and create links, the links look exactly like this:

<a href="http://www.date.com">Online Dating</a>
So then I looked at their FAQ under the question "How does Date.com track visitors from my site?" and their answer says:

Date.com uses cookies to track when a user comes from your site and signs up for a profile. Once a user signs up for a free profile, your affiliate ID is attached to that user for the lifetime of that user. If at ANYTIME they become a paying member, you are paid.
If there is no aff ID in the link, how can it get attached to the sale?