20m customers * 17% * 4 cents * 'x' transactions per customer = $136,000 * x I suppose this makes some sense. In a worst case situation, if every customer make

20m customers * 17% * 4 cents * 'x' transactions per customer = $136,000 * x I suppose this makes some sense. In a worst case situation, if every customer makes 10-20 transactions per year, and they always round down the maximum possible amount, they would lose millions per year.