Measuring time is hard, same as pockets.
Movement of numbers against the frame is the easiest.
Using number zero is the easiest but any number can be used.
Number 23 is at start diamond
After reference time the number 23 passed by ~1 pocket diamond marked with blue arrow.
Earlier there was a vertical diamond 1/4 of turn.
After it there is also vertical diamond 1/2 of turn away.
The blue one I call 1/3 even it is not the 1/3 of the wheel.
In the next measurement I can start again with any number at start diamond and check if after the reference time it is again one pocket from the 1/3 diamond.
That way you don’t have to have a timer that must be triggered in particular time but the free running vibrating metronome can be used.
Same principle can be used to clock the rotor for visual prediction.
For example if the reference time is 2 s and you predicting ~10s to the end of spin.
The time multiplier would be 10/2=5
It is the easiest to compare differences.
One spin the rotor made 2 pockets after 1/3 diamond , next spin the rotor made 4 pockets after 1/3 diamond so the difference is 4-2=2 pockets. Then is expected that the rotor makes 2 pockets x 5 multiplier = 10 additional pockets than in the previous spin.