Thanks MarkV, that makes sense.
If I don't use ticks but want to use prices, let's say I want the third favourite to be less than $7 and the fourth favourite to be greater than $15, would I word it like this?
AND third favourite's back price is equal or less than 7
AND at least one selection's back price is equal or greater than r_4_back_price, 15
Is that how to specify the fourth favourite's price? Note, I want it's price to be greater than 15 at the same time as the third favourites price is less than 7.