Nikon Z8 User Manual page 682

Option
[Center-weighted area]
G
[Display 5] consists solely of the information display and cannot be customized.
To complete the operation, press G.
Add an 8 or 12 mm circle to the center of the shooting
display whenever [Center-weighted metering] is selected
for [Metering] in the photo shooting menu.
The size of the circle varies with the option selected for
Custom Setting b5 [Center-weighted area]. The circle
is not displayed when [Average] is selected for Custom
Setting b5 [Center-weighted area].
608
Description
d17: Custom Monitor Shooting Display