Microsoft Monetize - Set split priority
If an impression applies to multiple programmable splits, the impression is assigned to the split with the lowest priority number.
For example, if Split A (priority 1) is targeting "domain=cnn.com", Split B (priority 2) is targeting "city=Boston", and an impression is available from a user in Boston visiting cnn.com, then the impression will be assigned to Split A because it has a higher priority (lower priority number) than Split B.
Go to the Split Details grid.
Set a priority number for each of your line item's splits.
The same priority number can't be set for multiple splits.