Strange Behavior in Current Influence Point after Champion Purchase

I have just finished a game and got 4883 IP in total. After purchasing Riven with 4800 IP, my account balance showed -4717 in the main page. To see whether the problem came from data fetching or actual IP calculation, I have clicked in a random champion, and found that the current IP correctly showed 83 remaining, I guess the problem should be the former. Attached is a screen capture from my computer for your reference.

Though I am just a casual player, I enjoyed this game a lot!! Hope you can keep up with the effort, meanwhile I am not making trouble here with a probabilistic phenomenon.