You already shot it? Didn't blow up in your face? Guess headspacing it doesn't matter much, then, all things considered.
It's a Forster gauge - you bought ONE, and it was the Field Gauge? Wrong one for you.
There are three headspace gauges, GO, NO-GO, and FIELD. Go gauge, chambers, NO-GO gauge doesn't chamber. They're usually sold in sets of both of them. That is what you need to determine in a new build - it clears the good one, doesn't clear the bad one. FIELD gauge is for in-service weapons ONLY, that are already functional. You ONLY use the field gauge on an in-service weapon that fails the NO-GO gauge. If the in-service weapon fails the NO-GO gauge, you test it with the FIELD gauge - if it DOES NOT chamber the FIELD gauge - that in-service weapon is still good to go. If that in-service weapon DOES chamber/eat the FIELD gauge - then you need a new barrel.
You used the wrong tool for this job...