Trying to understand the surface I see in perspective view

Okay, this is a little weird so bear with me. I want to map some errors in surface flatness in a physical surface so I will make measurements and input them by hand into a panel. The values that are there are just placeholders to get the program to work. (16.5 KB)

So the program creates a grid of points 2" apart. I break that up to calculate the distance between a zero point and all the rest. I take my angular error measures and find a height equivalent. All that works and I re-create the points now using the errors as Z. What I don’t understand is that when I create a surface from the points, it looks like i see more than one surface. What am I looking at? I expected to see a simple surface. Have I done something wrong or not set something correctly?

Input the number of points in U direction to get it working: (12.8 KB)

Thank you so much. I feel so much like a hacker with grasshopper because I don’t understand what the number of points in the U direction means. I really appreciate your posting a gh file with the additions so I can try to understand.