Is google ripping me off?

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I have recently set up and adwords account to advertise my website on googles sponsored listings section. My account with google states I have had 4,212 visitors today for which I am being billed £321.19. I have checked my webstats on my server account which states there have only been 3211 visitors of which just over 2000 come from google. Has anyone had a similar experiance with google or any of the other search engines I do not mind paying the bill providing its genuine. With my online counter and webstats both saying the same but google are telling me differant. If anyone has any advise I would be greatful