It depends...it is it is a throttle that try’s to hold 12-13 mph almost like a cruise control . It will slow down on a hill it will give the it a more power to try to make up for slowing down but it didn’t feel like full power or the motor doesn’t have enough power at that slow of a speed to give it lotsof push. That being said as all mileage claims on an ebike , your weight , wind , condition the size of your battery and other factors. It worked well enough for a couple miles when I fell and broke my leg ,couldn’t pedal and crank was bent too much to pedal anyway.
i would assume it would be approximately the same as pedaling at 13 mph casually. On a Stromer that could be up to 90 miles maybe on flat surfaces, just a guess what color battery do you have?