How are ad networks prioritized in the monetization stack?

The ad networks in the monetization stack are prioritized first by the prioritization that you set(12 being the highest and 1 being the lowest), then by CPM. For example, an ad request will always be made first through a stack item with 12 priority and a $0.10 CPM over a stack item with 11 priority and $0.20 CPM. You can learn more about prioritizing and the monetization stackhere.