Simply said, value describes the lightness or darkness of a color in a photograph. Value ignores the hue or color descriptions (blue, red, yellow), focusing instead on the tint and shade of the color; a tint is created by adding white to color, while a shade is created by adding black to color.
If you have the UHD version of 4K, you can multiply 3840 x 2160. This gives you 8,294,400 pixels, which is 8.29 megapixels.