Nikon Z 6II Reference Manual page 682

3
C : Adjust quick wireless control settings.
•
Choose the balance between
groups A and B.
•
Adjust flash compensation for
groups A and B.
•
Adjust settings for group C:
- Select [M] to enable or [––] to
disable the units in group C.
- When [M] is selected, the units in
group C will fire at the chosen
output.
Radio AWL
640