To make the process simpler .
Just divide the number of times it won at good tracks by its number of starts on a good track e.g. 5 starts for 2 wins=2.5/1=$3.50

Even if todays track condition is different to good,we still rate the figures purly on it`s good track performance.

If you try & rate it on say wet tracks ,using wet track form,it does not work well.

One might prefer to use the final figure as a price instead as odds ,so as to create more bets.
e,g 5 starts on good track divided by say it`s 2 wins =$2.50+ required

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Cheers.