Multiple Sub tiers on same account?

I have several different tiers of membership and it’s possible to sign up for more than one. For example I might offer THING #1 to Members at Level 1. But I also might offer an ADD ON of THING #2. So it’s possible someone has a Level #1 membership and an ADD ON #1 membership.

If i look at their account on my members page I see BOTH membership levels. Do they both renew? Does one have precedent over another?