Your overlay size does not match the tracked layer size, hence your coordinates do not line up. Effect coordinates are relative to the layer, not the comp. Pre-compose the graphic to a matching comp and/or adjust the keyframe values e.g. with an expression to add the required pixel offsets.
Many thanks for your quick response. I've tried to precompose the graphic and other things, as I try to understrand how this works. You can see that the corner pins are right, but the inlay showing up still wrong. I think I am going to follow the tutorial over again, because I'm still very curious what's wrong. Still a learning After-effects beginner, I guess. I will let you know when I succeeded.
it appears that you did not stretch the layer to the comp size, before you pre-composed it. make sure you are following these steps exactly:
1. place your 2D layer in the composition. delete all other information it has if you applied any - just reset everything.
2. now stretch the layer to the comp size by right clicking on the layer -> Transform -> Fit to Comp - (DONT WORRY About it looking a mess)
3. pre-compose the layer and select - Move All Attributes
4. apply the corner pin information to the layer from the tracker
5. be AMAZED
more about the process in here:
tried to find this straightforward process in there but could not. maybe you could
Take your replacement screen graphic and put it in a comp that is the same size as the footage you corner pin tracked. Now fit the original graphic to that comp using the Transform menu or the Keyboard shortcut Alt/Option + Ctrl/Cmnd + F. By the way, this is about the only time you should use Fit To Comp because it will usually distort your footage.
It will look distorted but that's ok. Now nest that footage in your original comp and apply your corner pin data. It should fit perfectly.
This should make sense if you think about it because corner pin is taking the track info from the entire frame and comparing that frame to the area you are tracking.
If your project is better suited to corner pin tracking in MOCHA there is an even better workflow that I demonstrate in this video: