Store co-owner Katie Devereux said the couple claimed their windfall about 9.30am yesterday.
"They were in shock. She thought they had won and the husband didn't. He didn't want to believe it until they had checked it.
"I asked them do you drink, and gave them a bottle of bubbly."
The checkout operator who sold the couple the ticket was the same person to confirm they had won, said Mr Devereux.
His employee's hands were "still shaking" when Mr Devereux arrived four minutes later.
"She had tears in her eyes after telling them. It's a really good feeling giving someone that news . . ."
The store owners are not strangers to giving such news. Saturday's draw was the third winning first division ticket to be sold at the store since the couple bought the business in April.
The owners celebrated the store's luck with a bottle of bubbly after being told of the win on Saturday night, Mrs Devereux said.
"Our Lotto area rep rang and said, 'Bloody hell, it was you guys again'."
Mrs Devereux and her husband were only slightly less shocked than the winners.
"You don't expect a phone call on a Saturday night saying you have just sold a $13 million Lotto ticket," she laughed.
They were "thrilled" the ticket-holders were Dunedin residents.
"That was the first thing we said when we found out we'd sold another winner.
"We just hope it's gone to someone local."
The other first division winners won $500,000 each and the store also sold a $2 scratchie worth $20,000 in May, she said.
Mr Devereux believed the store's luck was pure chance.
Regular customer of the store Richard Powell said he was pleased for the winners.
"Good on them. You hope it's a local, but you also hope it's yourself."
Lotto players in New Plymouth and Auckland also won $333,333 each in Saturday night's draw.
The $13.3 million win was the second biggest win in Otago since 1987.
The biggest was $13.36 million sold at Pak'n Save Dunedin in July.
