I believe it is a cumulative total of all participants. As they post their loss it also puts group totals.
DietBet Winnings: $151.43
Curvy Girl Challenge May 2013 (Runner-up)
MyFitspiration TWO! (Runner-up)
April Curvy Girl Challenge (Runner-up)
MyFitspiration's DietBet (Winner)
Fit for Life in March! (Winner)