If you know your gauge if off by x number of pounds, just use that number when you check your test your pressure.
No matter how much you spend on a tire pressure gauge, you should check it against one that you know to be correct. Eg tire shop, friend that races his cars.
That reminds me, one summer in the 1970s while in law school, I had a summer job driving a truck in northern NJ. There was one older driver there who knew nothing of the new interstate highways opening in the area, and always wanted to use the "old roads" on his route. As a joke, we gave him a 1959 road map as a "transitional learning guide" to becoming up to date on the new highways in the area.