Really? That's strange. You know I swear that I had gotten to level 22 and then went back to 21 and that the semi finished circle around the number indicating the proximity to the next level shrank a bit. Thought I had just remembered it incorrectly, but if the same thing happened to you maybe it was some kinda bug? To be fair, I'm not close to 100% certain that this happened as I wasn't paying close attention to it.