How can this be?

[Rex]

Has this happened to anyone? My average CPC is higher than my maximum set CPC... how can this be???

Rex

[Ofrika]

yes, it happened to me, and i was also confused - so i did some digging:

"User traffic fluctuates from day to day. To make up for these fluctuations and to ensure that your campaigns reach their potential, Google may allow up to 20% more clicks (or impressions, for cost-per-impression campaigns) in one day than your daily budget specifies. We call this overdelivery...

f Google overdelivers your ads, resulting in more clicks than your monthly budget allows, you'll receive a credit to your account..."

from:
https://adwords.google.com/support/bin/answer.py?answer=6145&topic=7029