Third attempt! I had a more accurate drawing to work with underneath- it definitely makes a big difference. Feedback would be appreciated!

I initially thought it was light reflecting off the sheets, probably from the lower right corner. But looking at the video I see hard edges on the top and bottom, which I think are closer to the light source- I think the arm is turned toward the source enough to catch a little bit of direct light.

I tried the assignment again with a different reference, and I think this came out better than my first attempt. Must keep practicing!

I think this is as good as I can do right now. Not sure if I should focus more on drawing more accurately, or painting, which is what I'm more interested in.