Pentax 645N2 Operating Manual page 83

[PF 8] Enabling/disabling displaying of the number of
films taken and frame counter in the viewfinder
The number of films taken and the frame counter are
displayed in the viewfinder while holding the Auto
bracketing selector to [ STEP ] position.
Pentax Function No.8
Disabling the display in the
viewfinder (initial setting)
Enabling the display in the
viewfinder
How to display
Hold the auto bracketing selector to [ STEP ] position.
The total number of films taken and the current exposure
counter are displayed in the viewfinder.
81
Number of films
Number of frames