Must have been one person clicking on the ad repeatedly. Google filters all but the first. But still once cent clicks SUCK though.
Sounds like the same user clicking on ads several times or possibly you clicking on it which doesn't give you any money but will stlil add to the # of clicks.
It's good make filter for the MFA site. Log on your google account and make filter. You can check MFA site here: http://70.87.49.210/~adsblack/ and put the data on your filter and wait 4 hours (google process). Have a nice day! Want get $200 click here...
This could be invalid clicks, maybe someone is bombing your site(s) ,you better send G an e-mail to report this problem, if not , they will flag you and this will result in banning, the issue is very serious!