This would be good information to have. It's kind of hard to tell, as the rested highlight can go off the current level and turn red, so the only way to know for sure is to burn all of it off but even doing that doesn't mean you were capped.

They need to add some sort of notification box/text while you are sitting in the inn, the % rested you are from the cap of when resting stops accumulating. That would be nice.