This tire inflator and gauge is showing you the pressure on the digital display in real time. That includes the pressure you are putting in from the compressor at the time you press the handle. Once you let the handle go you will see your tire pressure. If you go over your goal you can press a button to let air out. No disconnecting necessary to deflate or inflate. Gone are the days of putting air in and pulling it off and then using a gauge and the have to press the little needle in because you overshot. It has a clip to hold it on the tire stem leaving you free to use the other hand for something else.
The accuracy of a tire gauge can really be hard to measure. I've seen lots of reviews saying "this gauge is off" when comparing to yet another gauge. It's hard to say which gauge is off - however, accurate or not, this is as good as it gets. Make no mistake - this is a very fine tire gauge. I like the gauge read out a lot. It's big and bold, easy to see and read. The plus is it lights up which is something we all can use from to time.