The idea is you go back through the form and convert the odds to percentages.

So a horse starts at $1.80 previously, this equates to 55.55%
A horse that scores at this price receives 55.55 points.

So if we look at say the past five runs on horse A for example, the form might look like this

$1.80 - unplaced
$3.50 - 3rd
$8.00 - won
$1.60 - 2nd

In this example Horse A only won at odds of $8.00, so $8.00 converted to percentage is 12.50% - this horse scores 12.50 points

Horse B might look like this:
$1.80 - WON
$3.50 - 3rd
$8.00 - 2nd
$1.60 - WON

This horse won at odds of $1.80 and $1.60 previously.

Convert these odds to percentages in the same way as above.

55.55% plus 62.50% = 118.05 points.

If these two horses are in the same race this start, it shows that Horse A is a weak bet, Horse B is a strong bet.

Horse A only managed to win when not really fancied that well, and when it had the support of the public and very poor opposition by contrast, failed twice.
Horse B won as expected when well supported, lived up to opinion and ran as expected at longer prices.

It's just a guide to value...or lack of it.

Good horses keep winning, poor horses keep getting well supported and the money is always left with the bookie.

Hope this clears it up a little.

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