The competition required punters to go out on a limb and pick if a match would be a draw or nominate the winner, and whether the margin would exceed or fall below 12 points.
Walker bucked the trend by correctly picking Georgia to beat Tonga, and the mother of all World Cup upsets - Japan to topple South Africa.
Georgia's victory saw 35,000 punters fall off the list, leaving just 452 in the running before Ireland's clash with Canada.
Japan's stunning result meant the game was up by Sunday morning for everyone but Walker, who carried the hopes of a nation by himself for another 24 hours.
"I thought at this stage there would still be eight or nine thousand," said Stafford.
"I expected South Africa to not only win but win easily. That just cut us down.
"I was surprised how many people didn't take Georgia because they are a good side. So that was a killer blow and Japan was the fatal blow for just about everyone."
Stafford said the shock results of the tournament's opening weekend had opened punters up to the potential of the lesser-ranked sides.
Argentina had received some support for this morning's match against the All Blacks, with the reigning World Cup champions previously considered almost red hot favourites.
"It was really successful. Everyone's been talking about it. That result [Japan] has had an impact on betting patterns," said Stafford.
"What it has done is we have seen some money come in for the underdogs. People are now believing that the underdogs are a chance.
"We did see some money for Argentina against the All Blacks, and away from the All Blacks 13 and over and more into the 12 and under.
"We were delighted with the participation. Everyone got a bit of a buzz but we were expecting to last a little bit longer but what can you do."
