For grayscale, the output is the 8 bit value from the image mapped from min power to max power non-linearly, according to the sRGB power curve that images are stored in.
Min and Max are expressed as a percent in LightBurn, where 0 is off and 100 is whatever you’ve set on the panel.
So if you had an image with 0 and 255 in it, 0 would be output as Min Power, and 255 would be output as Max Power, both of those as a percentage of whatever you have set on the laser panel. They’re scaled, not clamped.