Entrants go through every pool match and pick their favourites to win and by how much - either 12 points or less or 13 points and over.
"The favourite to win by 13 or over is a pretty simple pick in about half the matches," said Stafford of the early pool rounds.
However there was always the chance of an early upset knocking many punters out before the knockout rounds began.
Stafford said for that reason everyone had a shot at winning the million, even the rugby-illiterate.
"Someone will go 'oh, I think Fiji will beat England' and if that [actually] happens, all the rugby-heads will be out."
All picks must be in before the tournament starts and no changes can be made after 11.59pm on September 18.
This is the second time the TAB is running the 'One Punt in a Million' competition.
The first was for last year's Football World Cup.
Stafford reckons someone has a much higher chance of winning the million this time around.
"At the start of the Football World Cup mathematically it was possible for someone to pick [it], but I would say the rugby one is infinitely easier ... there are going to be quite a few one sided games that are going to be easy to pick in the early rounds," he said.
"I think there will be a lot of people live going into quarter final stage with only 8 games to go."
Stafford said the chance of making the right predictions for every game was a one in a million shot, but "we are putting up a million dollars, it can't be easy to win a million dollars."
Stafford got a look at the million in cash earlier today, a surreal experience.
"I couldn't take the smile off my face really it was just like 'this is actually a million dollars' and I was hugging it," he said.
"It was like hugging a very big person ... who can't hug back."
How it works
• You can enter your picks at www.onepunt.co.nz, entries must be in by 11.59 on September 18.
• Changes to your entry can be made until this time.
• Entry is limited to people over 18 and there is a limit of one entry per person.
• Entry is free and TAB provide head to head odds for every match to help punters make their choices in pool play.
• A winning team and margin must be picked for each of the 48 matches.
• There are three margin options for every game, 0-12 or 13 and over or draw.