Canon EOS R3 Advanced User's Manual page 528

Specifying the Range of Images to Erase
While looking at the images in the index display, you can specify the first and last images for
a range to erase all the specified images at once.
1.
Select [Select range].
2.
Specify the range of images.
3.
Press the <
Select [Select range] in [
Select the first image (start point).
Next, select the last image (end point). A checkmark [ ] will be
appended to all the images within the range between first and last
images.
To select another image to be erased, repeat step 2.
> button.
: Erase images].
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