If you don't know how to manage 3 parameters then this doc won't do any good. But good luck in your path toward success!!
Parameters
-
Brightness (Percentage (-100% - 100%)) : The absolute value of colors (tones) lightness/darkness
-
Contrast (Percentage (-100% - 100%)) : The distinction between lighter and darker areas of an image
-
Gamma (Percentage (-100% - 100%)) : Adjusts the mid-tones from tonal scale, but keeps the white and black intact
Gamma may seem a more natural way to change the contrast while keeping an adequate brightness
Presets
Standard Presets: Light Contrast, Medium Contrast and Hard Contrast