Jerry and Marge Selbee, 80 and 81, sat down for an interview with "60 Minutes" and explained how they made $26 million through the lottery over nearly a decade.

Jerry realized in 2003 that he could almost guarantee making a profit playing a Michigan lottery game called Winfall.

Unlike Mega Millions, in which the jackpot keeps growing until someone draws all six numbers, in Winfall, the jackpot rolled over to lesser winners every time it reached $5 million.

The Selbees got so successful at the game that they set up a corporation and helped friends and family win too.

A small-town Michigan couple sat down with "60 Minutes" in January to tell the unlikely story of how they used "basic arithmetic" to find a loophole in the lottery that helped them win $26 million over nearly a decade.

High-school sweethearts Jerry and Marge Selbee, 80 and 81 respectively, ran a convenience store in Evart until they sold it and retired in their 60s.

In 2003, Jerry made a run to their old store and saw a brochure for a new lottery game called Winfall. Jerry, who majored in math in college, told "60 Minutes" he realized within just minutes that he could almost guarantee making a profit.

He explained this was because the winnings rolled down every time the jackpot reached a cap of $5 million. Unlike lottery games like Mega Millions, where the jackpot keeps growing until someone matches every single number, with Winfall, if the jackpot reached $5 million and no one drew a ticket with all six winning numbers, people with tickets that had five, four, and three winning numbers could cash in.

While that may be hard for some to follow, Jerry said that it's "just basic arithmetic" and that he thought others had figured it out too.

The first time he heard a roll-down was happening, he bought $3,600 in Winfall tickets and won $6,300. Then he bet $8,000 and won almost twice as much, he told "60 Minutes."

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The Selbees helped friends and family win too

Soon the Selbees were betting hundreds of thousands of dollars on Winfall.

They said they got so good at the game that they set up a corporation, G.S. Investment Strategies, and invited their friends and family to buy into the business for $500 apiece.

The group had grown to 25 members in 2005 when the state ended Winfall, citing lack of sales.

But soon after, the Selbees learned of a similar game in Massachusetts called "Cash WinFall."

A worker registers Cash WinFall tickets at a store in Massachusetts. Yoon S. Byun/The Boston Globe via Getty

For the next six years, the Selbees said they would make the 14-hour drive to Massachusetts anytime a roll-down was happening, buying hundreds of thousands of tickets at two convenience stores. They would then rent a motel room and spend 10 hours a day sorting the tickets.

But in 2011, their game came to an end when The Boston Globe received a tip that certain Massachusetts locations were selling large numbers of Cash WinFall tickets. The Globe's investigations team discovered that two groups were cashing in big on the game — the Selbees and a group of math majors at MIT.

The state launched an investigation but realized that what the two groups were doing was completely legal and that the state was actually making a lot of money through it. By then, the state lottery had decided to end the game anyway.

The Selbees said that over the nine years they played Winfall, their group won a total of $26 million and they made about $8 million in profit before taxes. They used it to renovate their house and help pay for the schooling of their six children, 14 grandchildren, and 10 great-grandchildren.

They also optioned the rights for their life story to be turned into a movie.