If you don’t want to do all of your reviews in a single sitting, you can just leave the page, but unless you’ve been lucky, you’ll have a handful of half-completed reviews where you only answered one part of an item, or you got it wrong and it’s still waiting to be completed and have its level lowered.
If you don’t return and complete those items within a certain amount of time (like 2 hours or something) then they reset and it’s like you never did any part of them before. This makes more work for you, with regard to the half completed ones, and could even result in getting an item right that didn’t deserve to go up, because you only got it right from having been reminded in the previous session.
The wrap-up button consolidates all your outstanding items into the next 10 so when you stop you have nothing half-done remaining. When those 10 are done the session finishes automatically.
We’ve known about this one for a bit, but it continues to be low on our dev priority list. We’ll bump it up a bit and take a look at it in the next few weeks.