I eagerly await an answer. I sure can’t figure it out.
I haven’t seen a CO2 regulator in a long time though. I don’t know what type of system you are dealing with. The only CO2 tank I’ve used was a crude way to make dry ice for the lab. I can’t imagine carbonation systems getting to 1500 psi, but what do I know. If this is a lab setting, I might suggest you have the wrong regulator, but it should still give a correct pressure I think. Most regulators won’t fit the wrong gas cylinders, but some will. If it is an old regulator it could just be wrong. This is especially the case in a lab where co-workers have been jimmying the mechanisms trying to figure out why it won’t fit onto the reverse threaded CO tank.