Active = accounts that have created username + password.
Inactive = accounts that haven't.

Mellow Ads to my understanding, like a-ads, only counts your websites unique views of users who haven't seen one of their ads yet that day.
Not to mention, numerous users use adblock as I don't block users from using adblock, which could also be part of those stats.

Furthermore Mellow Ads is showing the ad only gets viewed 9,000 times a day impressions wise, when Google Adsense and Bitmedia show I get 40,000 + impressions per day.