Admob fill-rate calculation

Noticed this a few times now. Admob’s listed fill-rate is always higher than it actually is for me.
For example:
Yesterday: 201,361 requests. 183,092 impressions. That is a fill-rate of 90.93%, but Admob has listed the fill-rate as 98.07%.
The same applies to most days as far as I can see. Now I’m not complaining about a 90.93% fill-rate. Anything above 90% is great, but why is their system lying to my face?

Looking back at data from August and September many days are displaying a correct fill-rate, but some are not and even have more impressions than requests(and showing less than 100% fill-rate).

Does anyone else have this problem?

Are Admob just lying to make things seem better? Or is there a bug in their reporting system?

My guess is that they only count the impression if the client confirms that the ad was displayed. Meaning, if the connection gets dropped after the request, or if the ad is “pre-loaded” but never shown, it counts as a request but not an impression. To calculate the fill rate they only count requests the server couldn’t deliver an ad for.