I don't understand why the number of ads changes.. For example in a large rectangle, sometimes it has 4 ads and sometimes it has 2... I always like to have 4 ads.. any idea why?
The ads are rotated ( think from an advertisers point of view ) Some times you get more ads for that block and sometimes you get fewer ads for the same block .
On the same page where I have both large rectangle and a wide skyscraper, I have more ads in vertical than that of rectangle.. The square have more ads too...but sometimes the square has only 1.. I think it's because of the viewer's origin..it may appear different to other visitors..
Use some logic The less ads you see the higher paying they are, right now my site has a few targeted advertisers and 1 block shows 1 ad and they are very high paying
If the top advertiser pays more than the following 4 all togheter only 1 ad shows. If the top 2 pay more than the following 4, only 2 appear. This was explain by a Google member in some Adsense video I couldn't find atm.