[jdangu]

My guess is that they have a script that observes ad placements and counts "non-impressions". Counting impressions at the site level is not the same as counting them at the ad server level. There are generally multiple ad servers daisy-chained into the ad tag, creating a lot of latency. It is very typical to lose 10% or more ad inventory simply because the ad can't load in time. If pagefair can't account for that, then the number is highly inflated.