ROI is referring to Return on Investment, or in other terms it’s profitability over time. This metric is calculated by taking the money won from a specific PRO system, dividing it by the money risked, and multiplying by 100.
The Bowl Season Betting Against PRO System shown below has an ROI of 14%, which is strong, given the large sample size of games recorded. This comes from the 19.33 units won divided by 133 games played—pushes are excluded—which gives us .1454. After we multiply .1454 by 100, we get 14.54, which is 14%.