I've been looking around, and I cant seem to find the answer. What I mean by that is, do cpm ads have to actually be viewed for a certain amount of time, or does it just have to be there. If I had a game app that popped up an ad everytime someone died and they clicked out of it in a few seconds would that count as an impression or would it need to be viewed longer for it to count as an impression. Also if the same ad is shown to someone multiple times is it still an impression?