Quoted from www.wired.com
"The key to the glitch was that under just the right circumstances, you could switch denomination levels retroactively. That meant you could play at 1 cent per credit for hours, losing pocket change, until you finally got a good hand—like four aces or a royal flush. Then you could change to 50 cents a credit and fool the machine into re-awarding your payout at the new, higher denomination."
Here is the whole article.
https://www.wired.com/2014/10/cheating-video-poker/
"The key to the glitch was that under just the right circumstances, you could switch denomination levels retroactively. That meant you could play at 1 cent per credit for hours, losing pocket change, until you finally got a good hand—like four aces or a royal flush. Then you could change to 50 cents a credit and fool the machine into re-awarding your payout at the new, higher denomination."
Here is the whole article.
https://www.wired.com/2014/10/cheating-video-poker/