Thanks for posting that, Jazz. I've come across this a couple of times now but still learning. And the machine translated Chinglish can be a puzzling thing!

The reason for having separate numerator and denominator might make sense if you have odd pulley ratios. For instance I have a 34t and a 60t, so the ratio is 0.5666666666666667 etc, whereas it is a simple 34 and 60 or 17 and 30 with no need to use a calculator.