I am curious to know is it normal or ? I found differences in "Total Earnings" row on reports overview page and detailed calculated through "top channels" link. Lets say when you login to AdSense you will see earnings for the current day and below a total as "Total Earnings" also you have a link to expand "top channels" which shows earnings from individual channels, now copy the data of top channels paste in MS Excel and calculate. Is there any difference in this and "Total Earnings" shown on main page. You will probably say that there is some delay in reporting but try same things with "last months" data or "since last payment" data.... still is there any difference? I have found difference in my reports..... is that normal or what?
For most people this is due to a delay in reporting.. Another reason might be that you have multiple channels being reported.. For example both a custom channel, and a URL channel that would report on that same ad-unit, or two custom channels.. Third reason is that Google is ripping-you off