Admob account showing big difference in matched requests and impression due to ad preloading

Question

Admob account showing big difference in matched requests and impression in interstitial ads as shown in the picture. (The last two rows).

I think this happens due to

Answer 1

This is normal. The difference is because there is not always an ad available (an impression) when a request is made. THis can be because of device, locale, time of day, time of year, advertising budgets.

The best way to ensure you always have an ad available to show is to use mediation and have 2-3 advertising networks in your mediation list.