I have not used this command before, but it seems like "UV range" implies that there is a minimum and maximum value for both U & V.
Here is something similar that I found, which shows an output with 4 values (min, max values of both U and V)
Thank you very much for the fast answer.
It did not work in a first try. As next step I will check the surface. Maybe this causes the trouble
UV parameters represent the boundaries of the surface you want to convert to sheet body. Untrimmed surfaces are infinite, but the sheet bodies should be finite. In the very rough explanation you can consider UV as the surface 2D coordinate system which follows the surface's curvature. Depending on you initial parameters you may found the UV boundaries in several ways. For example if you created a surface from the face you can get the boundaries via 2016 SOLIDWORKS API Help - GetUVBounds Method (IFace2) or you can map XYZ coordinate to UV parameter via 2016 SOLIDWORKS API Help - ReverseEvaluate Method (ISurface)
Thank you very much for your helpful answer.
I indeed missed the step of trimming my surface before creating a sheet/body from it pretty long.
I was finally able to solve my problem and the macro works fine now.
It took me a while, as the documentation of the functions messed up the difference between long and integer parameter.