One in 300.

That is the average number of blackjack dealers that professional gambler Gina Fiore discovered that flashed their hole card — or unintentionally exposed a portion of a facedown card that should stay hidden during the dealing process.

Working up to 16 hours a day scouting those dealers was well worth it to Fiore and her teams of advantage players. She said they used that edge to beat casinos in Las Vegas and around the world out of $15 million over 20 years, including $97,000 in cash that was wrongfully seized from her by a DEA agent at an Atlanta airport.

The former UNLV student and Green Valley High School graduate also overcame long odds to get her book, “Advantage Player: A Memoir of Blackjack, Backrooms, and Beginnings,” published. Fiore sent queries to 101 agents before she found one to represent her.…