@Jib, reasoning is good, but math isn't. You can't say you used 264 and gained 66, because out of those total 66 you need to actually use 36 to get to last rebate. Correct math in terms of value is (total gain/total spend)*100% ---> (66/300)*100%=22% gain. It doesnt matter if some of those scrolls to reach 300point come from rebate itself or were saved before- you need to physically use them to reach 300.

264 is a number of seals, that you need to save beforehand to be able to reach max rebate with the help of lower rebate rewards.

Correct way to say what you wrote is "spend 264 seals, get 36 from rebates, use them to claim last rebate. After all that, for saving 264seals you end up getting all rebates and additional 30 seals towards something else." Just a technical thing, but it's worth pointing out.