Can't work out how they do it, I have the number of races and added up the horse's winning and it agrees with the API I get automatically.

As far as I'm concerned this is not exactly a winning factor, so I don't use it, but still, it's intriguing what they do and why?

Although if I were to use it, I'd be inclined to use the last couple of years'
of earning at most, 12 months maybe a bit short, life time earnings may be utterly meaningless.
Just my opinion.