Hey alvin, to apply the value u obviously have to understand the form correctly. I think you should practive the forms rather than the values, when looking at your drawing. Try to draw the round form with contours and cross contours in the correct perspective. This will give you a better foundation to apply the values correctly.

Hey alvin, congrats on your first drawings. One of the things that will help you is if you squint at the reference so that you only see the shadow side and the light side. This will help you create form right away. I did a quick sketch to show you what I mean, I hope it helps :)