WP, "on" means it's less than even money which is 1/1.
1/1 means for each dollar you bet you receive another dollar = $2.00 you get back per dollar bet. Percentage wise it means the horse has a 50% chance of winning (1 out of 2 (1+1) )
So 6/4 on means 4/6 = you receive another $4 for every $6 you bet. So that's $1.67 back per dollar bet. 60% chance (6 out of 10 (4+6))
5/4 or 6/4 is then another $5 or 6 for every $4 you bet. ($2.25 and $2.50 respectively back per dollar bet. In percentage terms 4 from 9 chance = 44% and 4 from 10 chance = 40% respectively.)
Hope that makes some sense!
So Hutchy was saying it's 60/40 in Richmond's favour.
So all that means the good money is on Wallace coming to Tigerland.