Sony FX 6 Quick Start Manual page 75

Exposure: the Waveform Monitor
I don't tend to display the vectorscope or histogram in the VF. But I often
use the waveform monitor.
The waveform monitor shows luminance values in the image. It can be
read from left to right, exactly like the subjects in the image.
The lines on the waveform monitor from bottom to top are:
0, 25, 50, 75, 100.
0 is black and 100 is white.
The monitor shows values above 100 to 109, these are overexposed areas
of the image. Values below 0 are invisible.
Because the waveform monitor is so small in the VF, it helps to use Zebra
levels to hit precise targets.