That was one of the Achievements that was not backfilled. 505 is the number of ranked rounds you've had since the inception of G&A.
LVL 4 is the level you're working toward achieving now. So, once you get those 495 more ranked rounds, you'll complete LVL 4 and you should hopefully be done with that Achievement.
EDIT: Removed the misinformation about Achievement levels in general.