Divide trimmed surface

Hi everyone.
Please help me, I don’t understand the logic of trimmed and untrimmed surfaces. I created a simple circle in Rhino, in grasshopper made a surface out of it. It is displayed as “trimmed”. If I give the command ‘divide surface’, the number of points does not match the parameters. The same problem if I start to work with a surface after “split”. Saved geometry surface before ‘split’.
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Nurbs surfaces have 3-4 edges always. If not, they are trimmed. Your numbers do not match because the points that fall off the trimmed surface are ignored on the output. Divide surface divides the underlying untrimmed surface of a trimmed surface.

Thank you very much!