The qustion is  whether or not you can have more than three slots per page enabled for AdSense price optimization on a page, versus how many AdSense ads can actually serve. You can have more than three ad slots enabled for AdSense on a single page if the following criteria is met:

1. The ad slots are not exclusively showing AdSense, and other line items are rotating through the slots.
2. If at any time, you have three slots that exclusively show AdSense, and no other line items are targeting the slots, then it is your responsibility to disable AdSense on your other slots in order to adhere to the AdSense Terms of Service.