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Right, but if you consistently meet your budget, and you have many days where they overcharge, you will get decent refunds for their inability to gauge traffic? Correct?
In a word, correct. ;)
A related thought: It's worth remembering that if you often hit or exceed your budget, it is an almost certain sign that your ad will not be showing all the time.
This is because if you have your budget lower that would be required to show your ad all the time, the system will space out the delivery of your ad over the 24 hour day - by showing it sometimes and not others.