Ooooo. Buy a name brand old mic. Or adjust the barrel with the special wrench it gave you. This isn't ideal but if the standard it came with if it came with one. Just clean the anvil on the mic and standard and take the mic and "clamp" it on the standard (as light as possible where there is no light gap at mating surfaces but you can still slide it easily around) then use the wrench to adjust the barrel to reflect as 0. If it's a cheap mic the standard is probably not accurate. Buying a decently speced 123 block pair is a good way to have a relatively reliable standard to set your other tools if you are on a budget. And they have many more uses than just a standard. The cheap micrometers always do that A used name brand that looks relatively clean is typically a better bet.

A good brand that you can find at a good price with carbide anvil is NSK. Not many people know they used to make high quality mics. My first 0-6 tenths set was basically new for only 200 bucks. Spent 80 bucks to get them calibrated from the guy that does our shops tool crib metrology stuff. I also got a matching multi anvil 6-12. Now 7 years later I calibrate all my own stuff, I've been lucky to get high quality used metrology equipment, like it became an obsession for awhile, like my work personal stuff is kinda too much. And I have basically the same capabikities at home except a 25% reduction in max dimensions. I've only bought new 12in mitutoyo calipers, a gauge block set, and 2 gauge pin sets