This percentage is calculated by dividing the quantity of zeroes on the wheel by the total quantity of slots. https://gildenlow.com/%EA%B2%80%EC%A6%9D%EB%90%9C-%ED%86%A0%ED%86%A0%EC%82%AC%EC%9D%B4%ED%8A%B8%EC%9D%98-%EC%A4%91%EC%9A%94%EC%84%B1-%EC%95%88%EC%A0%84%ED%95%9C-%EB%B2%A0%ED%8C%85-%ED%99%98%EA%B2%BD-%EB%A7%8C%EB%93%A4/