Minimum time uses the interpreters minimum time instead of the customers minimum time. For example perhaps you pay your interpreters a minimum time based on the specific contract with the customer. You may have a customer A with a 1 hour minimum and a customer B with a 2 hour minimum. If you want your interpreter to use 1 hour and 2 hours respectively set Interpreter Minimum Time to OFF. If you have negotiated a set minimum time with your interpreter then position this switch to ON.