Whenever you earn something from AdSense, you see it gets reflected on your dashboard as estimated earnings. When we say estimated earnings, we mean that it's not final and may change when Google verifies it for accuracy. Earnings generated by any means of invalid or accidental clicks and impressions will not be counted while verification. The verification system is automated but also includes human reviews.
What is Invalid Activity?
Invalid click activity consists of any clicks or impressions that may artificially inflate an advertiser's costs or a publisher's earnings, and for which we decide not to charge the advertiser. This includes, but is not limited to, clicks or impressions generated by a publisher clicking on his own ads, a publisher encouraging clicks on his ads, automated clicking tools or traffic sources, robots, or other deceptive software.
Finalized earnings are accurate earning amounts you will be paid for validated clicks and impressions.
How Much you are Loosing?
Its now easy to find the difference between these two. At the end of every month, you can find out how much money you lost as a part of invalid activity. Starting with May's payment history, you'll be able to see the invalid activity deductions on Transaction history page under debits column.
If you are seeing a large deduction, make sure to minimise any unusual activity. However, if no amount has been deducted for invalid activity, you may not see any row for deduction.