Apple Color 1.0 - Manual (Page 173)

Chapter 9 Primary In 173
If the image is too dark and the highlights seem lackluster, you can raise the Highlight
slider to brighten the highlights, while leaving the shadows at their current levels.
Notice that the black point of the gradient’s slope in the Waveform Monitor remains at
0 percent after the adjustment.
Note: In this example, Broadcast Safe has been disabled, and you can see the white
level of the gradient clipping at the maximum of 109 percent.
If the highlights are too bright, you can lower the Highlight slider to bring them back
down, without worrying about crushing the blacks.