Tenacious, if you are just starting on this wonderful punting trip you may not be aware that most people rate horses in Kg (forgive me if I'm telling you what you already know). This is (probably) because in handicap races if a horse is better than those it is running against they tend to pile more weight on it's back to slow it down. Hence it seems traditional to say one horse is 5Kg (or whatever) better than another horse. Seems to me it would be more logical to say horse A is 1.5 lengths better than horse B but that's neither here nor there.
What this means is people go through the form awarding bonuses or penalties in Kg for each factor that may affect the outcome of the race. Like if you think barrier 1 is a big advantage give the horse in barrier 1 + 1Kg and maybe the horses in barrier 10 onwards -1Kg. Same for other things, like top jockey +1Kg, bad jockey -1Kg. What you end up with then is a list of weights against each horse. The top one may be 60Kg with the others having weights down to the bottom one at 52Kg for example.
These are the weights that people are now trying to convert to prices for you.

KV