JVC is apparently the only manufacturer that included CTL timecode capability in their video products, and this was limited to select professional S-VHS equipment.
These numbers are sometimes in real-time format (hours:minutes:seconds), but are often only an ambiguous 4 digit sequential counter.
These numbers advance up or down based on the machine counting a tape's control track pulses.
This type of display is useful only as a simple and temporary reference, as it is very inaccurate, and the counter is reset to zero when a tape is inserted.
A basic 4 digit counter is almost completely worthless, as their rate of advance was never standardized by manufacturers.