Thanks guys, yes I saw a few references to the idea that the Sky ratings points are based on 0.25 of a length but since the Tatts ratings come from AAP I am not sure if they have the same ideas.
Having been an AAP subscriber, I do know their ratings start out with a lower ratings score that then gets translated into a 100 point scale for Tatts.
e.g. first horse might have a rating of 42.5 and this gets moved up to 100 and all other horses in the race re-scaled accordingly.

I am curious to see the success rates of both the Tatts and Sky scales and see how they compare.