Nah the scale is unitless - you measure time over a known distance in whatever units you want, then it tells you the speed in those same units.
Eg. 1 mile in 30 seconds is 120mph but also 1km in 30 seconds is 120kph, although clearly they’re not the same actual speed.
They work over whatever distance/units you want - measure the time over the known distance and where the hand stops gives you a multiplier.