I revisited my post 210 in the DNA thread. While I was evolving my betting educations, I went through the PrePost phase and studied it fairly well:

Attached is a race worksheet from yesterday, Quirindi R8. I wanted to show you how prices change after Adjustments.

Take "Ima Secret", the winner. Original Pre Post price was $21 but that was based on a 170% overround. By the time you increase the % share of the field to make up for the four scratchings (in red) and then reduce the % to a 118% overround the Pre Post is now $12.55. Big jump from the $21 that it started off in the paper.

Rule 1 signals "LAY if OPEN > Adj Pre Post 118%"
Rule 2 signals "LAY if FINAL FLUC > Adj Pre Post 118%"

I filtered those signals with selection criteria and Lay bet Right Vintage & Cadel's Luck.

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You'll have to go to the thread for the attachment