I was awarded the Mortarboard badge for my SO account today, but I've only received 95 rep for the whole month. Why did I get it?
The badge was incorrectly accounting for deleted questions/answers, with a little bit of confusion added by the giant recalc that happened over the weekend.
The good news is; you no longer have this incorrect badge! woo! (that is success, right?)
This badge is retroactive, so if you earned it at any point in the life of your account, you will get it.
This can also be affected by retroactive deletions (posts + users + votes).
See http://stackoverflow.com/reputation for more.