It is supposed to show this on the screen at least, shortly after you begin charging, and it will move your limit down to 80%. You can then raise it after that. I don't know if it also sends a notice to the mobile app or not--haven't had a chance to check. It's possible some notifications got messed up or didn't get sent. Or maybe the status of that site changed to high use after your charging was going. I don't know how that would be handled.
I just wanted to clear this up to not mix two things. The 50% thing is different than the high use locations with the 80% limit.