Visualizing contours on top of DEM

I am new to Global Mapper and I have raster DEMs in .adf format. I opened them in GLobal mapper. I also have contours on the same area.
When I open the contours on top of the DEM and get the 3D view, then I saw two lines for the contour. One is projected onto the surface. Other line going by touching the 3D surface and some line parts are going without touching the 3D surface.

I am now confused what is the correct  contour line that I should consider. And why 2 lines are given by the Global Mapper?

I also want to know whether we can do some sort of analysis like, computing the height differences between some given location to what is the height from the raster DEM?

Please comment me. thanks
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