it is because you haven't played in 6 months, and we've changed lobbies since. you haven't won a game in main lobby yet. It'll look a bit more normal once you do. If you had won all your games and not lost any it would be the opposite situation
The main lobby is a new lobby id so the piechart is specific to your wins in that lobby.
ok now it's just weird in other ways. it shows 75% loss