Google total has page impressions so I wondered if two ad blocks counted as one or two page impressions?
In main statistic it counts page impressions, but in advanced reports you can select ad block impressions or ad impressions.
I had this question before. But if you have 2 banners that showed something differently on one page view, then it would count as two impressions.
All depends on how you're viewing your statistics. There is a drop-down list to let you choose. It could either be 1 impression, 2 impressions, or 8 impressions (assuming there are 4 ads in each block) Check your Advanced Reports options.