Right now I’m sitting on 0XP progression into the next level and I certainly gained far more into the next level, I did not hit the level barrier perfectly.
Or the xp boost just ran out and you did infact only get 400xp. I think they only count if you still have time left at the end of a match (which is really annoying!), so if you started the match with 5 mins left & it’s a 6 minute match it won’t count.