The rule is surprisingly brutal on long-odds Jewels runners, making coupling them up with themselves in earlier races plain stupid.
For example, if you wanted to back a pacer to win at Alexandra Park on Friday at $2 and multi-bet it to win at the Jewels at $31, the actual bet would be calculated at $2 and $10.13.
That is because the TAB computer uses a formula which detects the fact the first bet winning could affect the odds for the horse at the Jewels.
The process affects punters less the smaller the Jewels dividend. For example, if you coupled up Escapee to win a race next week into the Jewels and she won the first race, her Jewels odds would only diminish from $1.50 to $1.44.
The important catch for punters to understand is that the deduction in Jewels odds is the same whether the horse wins a maiden at Timaru or a group one at Addington.
The way around it is to back the horse to win the first race and then if you are keen to back it to win the Jewels reinvest after the markets reopen.
"It is standard practice for many bookmakers overseas but it is worth noting for punters," said TAB bookmaker Steve Richardson.
Many of the Jewels markets have a confused look about them, with the juvenile male pace having been hit hard by withdrawals and every major juvenile fillies' race having been won by a different horse.
The 4-year-old trot has seen local star Paramount Geegee pull out while the 2-year-old trotters are incredibly even.
One of the value bets 3 weeks out looks to be Stent in the 3-year-old trot.
He opened at $6.50 and could have a big advantage over stablemate Escapee ($1.50) as she will have to start off the unruly, which won't be a lot of fun over a mile at Cambridge.
Meanwhile, Twist And Twirl should put her campaign on track when she contests the Nevele R Final at Addington on Saturday from the ace.
She was beaten at Ashburton on Sunday but takes plenty of work and her $3 odds for the Jewels may be gone this time next week.
