It is sorted by clicks so that you can ban ad units that generate too much useless traffic for your site.
It isn't.
http://i.imgur.com/7uDvnWp.pngLooks kinda random.
Also, for freebitmoney.com statistics shows 181 impressions, while impressions column shows 921. Which is right?
Thanks for your question.
If you hover column names, you'll notice that Clicks and Impressions columns show non-unique clicks and impressions, whereas Statistics columns shows charts for unique clicks and impressions.
Clicks/impressions columns represent amounts of clicks/impressions during a month, but the table is sorted by amount of clicks during a day (it allows to quickly identify and block main sources of recent load on your site).
We'll work to improve the interface, I've added the feature request about custom sorting to our issue tracker.
