Number can vary from about .25 to about 5.0. Higher is darker.
Default is the word "default." It returns the display to its normal setting.
The setting lasts until you reboot or change it again.
A setting of 1 is neutral. Lower is lighter and higher is darker.
If you set a number that's too high or too low for your video card, HotkeyNet will say that Windows reported error 87.
When the argument is a number, HotkeyNet sets a curved gamma ramp.
When the argument is "default," HotkeyNet sets a linear gamma ramp from pure black to pure white.