The Black Level setting controls the 0-15 chunk. The Super White setting controls the 236-255 chunk. It all depends on what your display supports and if you are sharing that input with other devices through a switch/receiver that will spit out the same levels. Safest is 16-235, Black High, no Super-white. Everything supports that, and it matches the default for component if you are doing some component-to-HDMI upconversion for like a Wii through a receiver, in example.