With Cell Shading, instead of continuous shades, you map, or approximate, intervals of shades to be a single flat colored shade. The underlying ideas are all the same; you should shade by paying attention to the light source and the surface receiving the light.
With your attempts above, you've failed to correctly represent the surface of Kent's head which lead to his head looking like a flat cookie.
With your attempts above, you've failed to correctly represent the surface of Kent's head which lead to his head looking like a flat cookie.