Unless it's a tiny ark welder 30 amps seems a bit low. Ark welding in an auto body shop is not an acceptable repair by todays standards. Are you sure it was not a MIG welder? I could see the nameplate on that being 30a.

What do you mean they have service for other equipment?
Is there is 2 services for the same unit and one service your talking about is only for the equipment you listed?

Besides lighting, office, breakroom, bathroom, HVAC, there are receptacles in the shop? Is there some kind of exhaust fans in the shop? Things might be used like battery chargers, power tools, hydralic pumps, stud welder, portable heaters, work lights, fans, resporator pumps, and even computers.

Loads to come might be a frame rack, spot welder, plasma cutter, TIG welder, paint mixer, etc.

Paint booths have lighting, a large fan(s), and a heater that can bake the paint. 23 amps sounds a bit low for FLA.