It isn't as much to claim specifics about what you do wrt targetting. It is to try prove they have engaged users who are looking at the screen rather than, for

It isn't as much to claim specifics about what you do wrt targetting. It is to try prove they have engaged users who are looking at the screen rather than, for instance, opening it in a tab then closing it later without ever reading any of it. You might link that to what adverts were shown, but only if they know that information (they may not if the advertising space is farmed out to 3rd parties which is very common).