Nikon Z 8 Reference Manual page 594

D
File Number Sequence
If a picture is taken when the current folder contains a picture numbered 9999, a new folder will be
created and file numbering will restart from 0001.
When the current folder number reaches 999, the camera will no longer be able to create new
folders and the shutter release will be disabled if:
- the current folder contains 5000 pictures (in addition, video recording will be disabled if the
camera calculates that the number of files needed to record a video of the maximum length
would result in the folder containing over 5000 files), or
- the current folder contains a picture numbered 9999 (in addition, video recording will be
disabled if the camera calculates that the number of files needed to record a video of the
maximum length would result in a file numbered over 9999).
To resume shooting, choose [Reset] for Custom Setting d7 [File number sequence] and then either
format the current memory card or insert a new memory card.
D
Folder Numbering
If a picture is taken when the current folder contains 5000 pictures or a picture numbered 9999, a
new folder will be created and selected as the current folder.
The new folder is assigned a number one higher than current folder number. If a folder with that
number already exists, the new folder will be assigned the lowest available folder number.
594
d7: File Number Sequence