Canon EOS 1D Mark II N Instruction Manual page 77

Continuous
The file numbering continues in sequence even after you replace the
memory card. This prevents images from having the same file number,
so image management with a personal computer is easier.
File numbering after
changing the folder
Memory card 1
100
XXXX0001
If the memory card in use has a DCIM folder, the file numbering might
continue from the last image saved in the folder.
Manual Reset (M-Reset)
This creates a new folder automatically and resets the file number to
XXXX0001. Images captured thereafter are saved in this new folder.
The file numbering method (Auto reset or Continuous) that was in effect
before the manual reset will continue to take effect.
File numbering after replacing
the memory card
Memory card 1
101
XXXX0002
3 File Numbering Methods
Memory card 2
XXXX0001 XXXX0002
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