I'm not very versed on that subject 
could you please explain the difference between high and low?
its a Ratio (math) tooth count front, turns tooth count rear, by multiplication..
(or small divides into large by those numbers )
then you multiply that by the wheel diameter in inches .
that, in a common way to perceive it, is Gear Inches
[as if it were 1 big drive wheel on like a penny farthing bike]
the factory has 12, 13 15 & 16 t cogs (maybe a 14 too) .. and 3 chainring choices 44, 50 & 54t
44:13x16" is about 54" 54:12x16" =72
if a 3 speed IGH like the BSR then that gear can be made 3/4 or 4/3rds as small/big
by the internal gears in the hub,,