Screwed into the tire valve. And the reading was 18. Is that what is in the tire.
Seems terribly under inflated am I using the compressor in the correct way.

If the gauge is accurate, that is what was in the tire. Personally, I never rely on those gauges. I use a simple tire gauge available at most parts stores.

Hi,
I agree with the separate tire gauge aanswer. I would point out that the inflation amount depends on the tire usage. Outdoor power equipment uses 14 psi in front and 10 psi in the rear, as a general rule. Automotive tires generally use 30-32 psi for the older(normal) tires and I have no idea for the newer tires with the reduced sidewalls like the 18 and 19" tires. A good rule of tumb is to look at the lettering cast into the very sidewall of the tire. There it will have the Max inflation pressure cast right into the tire.
Most tires can be over-inflated to some extent safely. OPE tires, though they are 14 and 10, will be shipped strapped down and inflated to 25-30 psi to secure them in the crates for shipping.
Peace,
Clarke

My son used it last night. My old inflator didn't have a gauge. In addition I have two never used tire gauges. Put 30 pounds each tire.Car feels like I have power steering. Great
Thanks for the help