I thought that users received only 10 flags per day. Has this policy been changed (probably not) or is there some other bug that is causing this?
The base amount of flags per day is ten but you get more per day as a reward for having more reputation or good flagging history - up to 100 total flags per day.
If you read the flagging privilege page a bit more closely you'll see it says all the way down at the bottom:
How many flags do I have?
When you start out, you are allotted 10 flags per day. This number may increase to up to 100 flags per day:
- You get one bonus flag per 2000 reputation.
- You are awarded additional bonus flags when you flag correctly - one bonus flag for every ten net helpful flags (helpful flags minus declined flags).
You have 13 net helpful post flags, so you get one extra flag per day - 11 total.
No bugs here.