I just watched your video. When you have >7mm sticking out, and you pushed it in against the spring pressure and it stopped going in, that was when your valve was seated. That's what causes it to stop... the valve seats, and it can go in no further. That's when you take the measurement. If you watch your video, it looks pretty close the ~6mm (or the 5,85mm it was before) when you push it in and the valve is seated. When you release the finger pressure holding it in, the spring is pushing it back out to >7mm. If the front of the rod is moving forward, so is the back end by an equal amount, so your valve is opening by the same amount the rod moved forward, and the >7mm measurement is being taken while the valve is not closed. You want the measurement taken when you push it in until it stops (valve is then seated closed). That doesn't look like it was very far off, since you look to be pushing it in ~2mm to seat the valve against that spring pressure.
When you get it all back together, the valve spring should overpower that little bit of hammer spring pressure holding the valve open. Looks like you should be fine. Let us know!