Hi BGHWAN. In its original version The 10 point plan made no mention of doubling the average price of winners to get the divisor but its a good thought.
What it was set up for really was multiple betting .
TARGET - DIVISOR 10 DIVIDED INTO THE NUMBER OF SELECTIONS.
i.e Target $100 divisor 10 = $10 (3 selections in the 1 race = $3 on each.)

The correct formulae for deciding MAXIMUM /MINIMUM DIVISORS is
EXPECTED WIN ODDS X EXPECTED STRIKE X .08(thats point 08)
THE MINIMUM DIVISOR IS YOUR EXPECTED WIN ODDS.(but never below 2 )

In the case of say 3/1 and a win strike rate of 31% X .08 = 7 MAXIMUM DIVISOR and 3 as a MINIMUM DIVISOR.( I always take it to the nearest whole figure.)

Cheers.
darky.