So once your pump gauge starts reading, it is usually reading the pressure in the tire. You usually hear a little whoosh when the pressure in the tube of the pump exceeds the tire pressure. Reading the gauge when you hear that will tell you the approximate pressure in the tire. You can always remove the pump and depress the center portion of the valve to let air out of the tire if you are afraid you have overinflated it. So - if you want the tire to be at 110, you would pump until the gauge on the pump reads 110. Make sense?