Canon EOS RP Mirrorless Camera - Manual (Page 365)

365
File Numbering Methods
Auto Reset
When you wish to restart the file numbering from 0001 each time the
card is replaced or a new folder is created.
When you replace the card or create a folder, the file numbering restarts
from 0001 for the new images saved. This is useful if you want to organize
images by cards or folders.
If the replacement card or existing folder already contains images recorded
previously, the file numbering of the new images may continue from the file
numbering of the existing images on the card or in the folder. If you want
to save images with the file numbering starting from 0001, use a newly
formatted card each time.
0051 0001
(1)
File numbering after replacing the card
100
0051
101
0001
File numbering after creating a folder
Card 2 Card 1 Card 1
(1) File numbering is reset
Manual Reset
When you wish to reset the file numbering to 0001 or to start from file
number 0001 in a new folder.
When you reset the file numbering manually, a new folder is created
automatically and the file numbering of images saved to that folder starts
from 0001.
This is useful, for example, if you want to use different folders for the images
taken yesterday and the ones taken today.