The Minimum an Maximum Shipping Rate Settings feature will set thresholds so if a calculated shipping rate is outside of the thresholds that have been set, either lower or higher shipping rate will be charged based on those thresholds.
For example: An order is placed and the shipping calculates at $20, but you have set your maximum shipping rate threshold at $15. The order will be charged the maximum allowable shipping rate of $15 – not the calculated $20
