Ad opportunities (also known as "historical ad opportunities") are the number of times it was possible to have delivered an impression in the past, even if there was no actual impression for an ad request.
How ad opportunities are calculated
Ad opportunities = Total impressions + (Unfilled impressions × Impression rate)
The "Impression rate" multiplier accounts for the fact that Ad Manager counts network-level ad impressions using the downloaded methodology and mobile app impressions when the creative is displayed on screen. Using this multiplier with "Unfilled impressions" provides a more accurate picture of missed impression opportunities.
Example
For network traffic with 95% of served impressions that are also downloaded impressions, the impression rate will be .95.
