The story sucks to be honest. First of all because of the percentage you mention, but is there that much difference between $5,000 and $27,000? If he had said that $5,000 got him $500,000, it would seem to me to be a considerable difference.
And besides, it was the only way he could get that $22,000 difference? I don't know, maybe taking a loan to invest in his company would have made more sense.
The meaning behind the story isn't about the winnings but the motivation he gets from winning in his gambling session. Take note Smith was feeling down due to his company's problem when he went to Las Vegas to play in a Casino. But due to his winnings regardless of the amount, he finds motivation within that experience. And that motivation gives him enough strength to face the company's problem, solved it, and eventually made it a successful venture.