Ah, your Facebook account isn't linked to your Army.ca account. I'm not sure what your AO Facebook account is but it must have earned the 500 MilPoints bonus multiple times. You likely spent it on equipment and so when the adjustment happened, it put you in the hole. If you want to PM me your Facebook account name I'll take a look and see what I can do.
Cheers
Mike
Edit: One thing I could do is link your accounts... MilPoints you earn here (and you have 3,300+ already) would then be accessible in the game.)