I'm working on establishing a nether hub in 1.18.1 on my server. I have a portal in the overworld I am trying to link to a portal in the nether ceiling. To make sure the coordinates are right I am using position of the left of the two bottom obsidian blocks on the portals (making sure I am facing the same direction of course). The block on my overworld portal is located on 720/-11/-1320. So I placed my nether portal on 90/128/-165.
However when I light the portal on the roof instead of linking up to the portal i want to, it generated one on a tree located at 730/109/-1320.
I have tried moving the portal a few blocks on the ceiling a few times, and it has generated more portals always on trees always pretty close to the same area.
Are my calculations incorrect, and how do I fix this?