Shawn is absolutly correct, however you'll need a very accurate pressure meter for that kind of response. Typical meter are not spec'ed to that tolerence otherwise it would be expensive and your car would double as a weather station. I suggestion is not to worry too much about that, just understand that the meter is a lose approximation of pressure, as long as it is not WAY off the car spec'ed as stated in car manual. However you can get a good pressure gauge and get a reliable reading. Then you'll know the offset of your meter.

Haven77