A useful way to measure, and a good rule: move the promise to line two. A real question from someone who just got burned on measuring: how do you count 'stayed past 3 seconds' and 'read to the end' on a plain page without a tracker? My own counter turned out to be inflated by my own checks, so I'm now careful about which numbers I trust. Did you add a script of your own, or does the platform give you these figures?