new rules on show payoffs

we had a horse today in the first at Turf Paradise who had over 20,000 to show on it. the show pool was 21,000. it won and his payoff to show was 2.10, but the other horses payed 2.60 and 3.00. what is the name of this new way of show payoffs and how does it work. i tried to remember, but couldnt. in the old days, all the horses would have payed 2.10, but not now. something like net pooling or such.