Canon EOS-1D X Mark III Advanced User's Manual page 291

Movie Play Count
You can select how time is displayed on the movie playback screen.
Rec time
Displays the recording or playback time during movie playback.
Time code
Displays the time code during movie playback.
Note
Time codes are always recorded to movie files (except for High Frame Rate movies
set to [Free run]), regardless of the [Movie rec count] setting.
The [Movie play count] setting in [
play count], so that these settings always match.
The "frame" count is not displayed during movie recording or playback.
: Time code] is linked to the [
291
: Movie