Thanks for your help. That makes sense about the center option and for the magnitude and distance for inter-rater.
I think my questions is similar to this post: A bit of confusion about the slicer coordinate system.
I checked my settings and confirmed that patient right is screen left. In the picture I uploaded you can see for the same landmark, patients 319 and 320 in have x,y,z coordinates different than every other patient. Why is this happening only for 319 and 320?