Nikon Z fc N2016 Reference Manual page 133

Exposure indicators
D
･ The difference between the exposure value resulting from your setting
combination of the shutter speed, aperture, and ISO sensitivity, and the
appropriate exposure value measured by the camera, is displayed in the
monitor and viewfinder. These "exposure indicators" are displayed as
follows.
Display Optimal exposure
Monitor
Viewfinder
･ If exposure compensation was performed in mode M, the reference value
for proper exposure in the exposure indicator changes.
Exposure warning
D
The displays will flash if the selected settings exceed the limits of the
exposure metering system.
The mode selector
Underexposed by
/ EV
1
3
133
Overexposed by
over 3 / EV
1
3