aftergame progress report/stats bug?

I played a game and got 31 kills but in the aftergame progress report it only gave me 28 kills. I thought that was strange so I went in theater and counted every kill I got and ended up at 31. when I held the back button in theater it even said I had 31 kills, but on waypoint and the aftergame progress report it was 28.

Anyone know what this is and why it happens?