Does the Ad Delivery Report show billable clicks only? Where are the invalid clicks coming from?
The Ad Delivery Report, like every other performance report, displays only the valid clicks for which you are charged. Our Click Protection System uses a variety of techniques to filter clicks before they show up as a charge on your reports. This software is working 24 hours a day, seven days a week, and as a result, you may receive clicks for which you are not billed.