i was using the level up system |here|, and when i clicked "confirm/continue" the page just did not load; it spun around on the loading logo for a moment then jumped to "gateway timed out" and i had to refresh manually as it was just stuck on that error page. By the time i had the |Spend EXP| page pulled back up, it did not give me the levels, it took the EXP, AND put me into the negative somehow lol
This can happen when it 'double spends' the EXP amount and gives you double the stats by accident. You can file a ticket and ask a staff member to confirm if you got the stats you paid for, but usually it's nothing to worry about. As you earn more EXP, it'll go back into the positive. It basically just acts as a temporary loan until you earn more EXP.
If it ended up giving you no stats at all, I would definitely file a ticket so a staff member can award them to you.