An Urbandale man has been playing the same set of numbers hoping to win the Powerball jackpot for the last two decades.Lottery officials said Robert Winburn's strategy paid off during Saturday's drawing.He won a $1 million prize in the $330.8 million jackpot by matching five of the winning numbers.Winburn, 49, said he assigned numbers to the letters of the alphabet and used the corresponding numbers in his last name as his Powerball numbers.  Up until this point, the strategy had netted only a $100 prize for Winburn.No one matched all six Powerball numbers on Saturday, which pushed Wednesday's jackpot to an estimated $400 million prize or $227.8 million cash option.Winburn said he learned he won by using a self-check station at an Urbandale Git-N-Go store."I put the first three (tickets) in and no win," Winburn told lottery employees Tuesday. "Then (the winning) one came up. I just kind of glanced at it. I did tell the guy next to me, 'I don't believe this,'"And he leaned over and I did it again and he says, 'Sign it and get the heck out of here.'"The odds of winning the $1 million prize is 1 in 5,153,632.65.