Photo No back to zero

FILE NAME..................................................Resetting the file names of pictures
RESET This method is useful when grouping files on separate cards.
The file number and folder number are reset every time a new card
is inserted in the camera. The folder number returns to [No. 100]
and the file number returns to [No. 0001].
AUTO This method is useful when you want to manage all your files
with sequential numbers.
Even if a new card is inserted, the folder number and file number are
retained from the previous card. This helps you to manage multiple cards.

To do this you go to the menu and to the setup option and press ok. Down arrow to file name and pick the option you want to use and press ok.