Each line is an original price followed by one or more discount rates; the result shows the final price, the amount saved and the effective rate. Successive stacking compounds rates the way shops apply an extra discount on an already reduced price (20% then 10% = 28%); additive stacking simply sums them. Reverse mode takes the final price and the rates and recovers the original price. Rounding is half away from zero at the chosen decimals. Everything runs locally.