Why the two fiducial points have the same value?

Dears in 3D Slicer support team,
I am using 4.11.2021.02.26 version and after doing Pick’n paint, model to model distance, and mesh statistics for measuring the distance different of two different time CT created surface models two fiducial points have the same value!!!
why this happened?
Although, in the second point determination I restarted 3D Slicer again, but with the same results?
2. What are the differences between the region considered drop list that is showed in the screenshot below?

Thank you so much for your sincerely appreciated help and support.

I think you need to check if the points really match, if that happens there is no error it just means the points are equal

Hope it helps

Thank you so much for your reply. Actually, the two points are different as the location is not the same, and when I closed the 3D Slicer and reopened it, and did the other point again, the values are different…
So, the problem now is every point I need to measure its value, I need to close and reopen the program which is not convenient… Please I need to have a good idea about using Q3DC module, as I heard that it can do the same function of pick’n paint!
Thank you again for your help,

I dont kn9w about qcd3 module but i’m sure someone here will help you