Deck position on the mapALEvents

I am trying to reposition a deck on a map using the “reposition stack” tool. But what I get (image 1) does not correspond to what I have asked for (image 2). It seems to be displaced to the top and left. Am I missing something obvious there ?
Thanks for your help !
Capture d’écran 2024-03-05 à 17.32.07