CTR has different meaning depending on your ad unit
Pop / interstitial (DSP, myDSP)
It is the percentage of the available market you get through the bidding system. That’s why here, the CTR is your win rate, i.e. the percentage of pops you got vs the bids you made (click/impression).
For example if you get 5% of CTR, you have won 5% of all the bids you made.
Push notifications (push.eureekkaa)
It is your click rate on your impressions.
For example, if you get a 0.8% CTR, you have 0.8% of notification viewers that click on your notifications.
A "normal" CTR on push notification is between 0.5% and 1% (July 2020)