Google Adwords charged way more than I thought it would?

[jake p]

So I started a Google Adwords campaign just to get my videos a little bit of a push. I set the average cost per day at $2.00. And I put $20.00 in my Adwords account. So my impression of it was that it would run my ads a little bit for 10 days and be done. Well I had my Ad going for about 12 hours, wake up this morning, and my video gained about 3,000 views. I was pretty happy. Then I went to my Adwords account and checked my statistics, and under the Total Cost column it says $147.09. Wtf?? What happened? Am I just completely oblivious to how Adwords works? I thought by putting $20 into my account I would only be charged a maximum of $20. Now I owe $150..