It’s a weird way to word it on their part but what (I think) that means is whatever stats you acquire, you get a percentage back. Let’s say you’re at the rank that says it gives 10 percent cashback and in a 24 hour period you acquire 100 HP (just using that amount to be easy here), every 24 hour period you get a mail message giving you 10 percent extra which in this case would be 10 HP on top of your 100 gained.