A number of forums have noted that Google's AdSense reporting is having problems. Yesterday webmasters were noticing discrepancies in basic impression numbers between AdSense and their log files.
The problems appear to be tied to the Custom Channels statistics, according to most comments.
A comment in Google Groups by a Google employee indicated it had nothing to do with the announced changes to AdSense yesterday. "Our engineers and product
team are aware of this aggregate vs. channels reporting discrepancy.
They're working as quickly as they can to fix the issue, and I'll let
you know as soon as I find out more.
FYI - This is unrelated to the announced product change from the blog
yesterday (that feature hasn't launched yet)".
Anyone seeing the same thing in their accounts can discuss it here.