first time to see this on my account: so what is this exactly? i can not track any ad unit until now can you explain it according to this feature ?
From what I gather, after reading what was on "Learn more...", a single ad unit can be assigned to more than one channel. This is a pretty neat idea, as it allows much more sophisticated analysis of your ad performance. If you don't know about channels yet, then you should read this. Cryo.