Always assumed rule 4 was a fixed deduction?
ODDS DECIMAL DEDUCTION
1/9 or shorter 1.11 or shorter 90p in £1
2/11 to 2/17 1.18 to 1.12 85p in £1
1/4 to 1/5 1.25 to 1.20 80p in £1
3/10 to 2/7 1.30 to 1.29 75p in £1
2/5 to 1/3 1.40 to 1.33 70p in £1
8/15 to 4/9 1.53 to 1.45 65p in £1
8/13 to 4/7 1.62 to 1.57 60p in £1
4/5 to 4/6 1.80 to 1.66 55p in £1
20/21 to 5/6 1.95 to 1.83 50p in £1
Evens to 6/5 2.00 to 2.20 45p in £1
5/4 to 6/4 2.25 to 2.50 40p in £1
8/5 to 7/4 2.60 to 2.75 35p in £1
9/5 to 9/4 2.80 to 3.25 30p in £1
12/5 to 3/1 3.40 to 4.00 25p in £1
16/5 to 4/1 4.20 to 5.00 20p in £1
9/2 to 11/2 5.50 to 6.50 15p in £1
6/1 to 9/1 7.00 to 10.00 10p in £1
10/1 to 14/1 11.00 to 15.00 5p in £1*
Over 14/1 Over 15.00 No deduction