The fire extinguisher is not just for show
They aren't. Those are the codes utilized in the Priority Dispatching™ system by the National Academy of Emergency Dispatch™ (NAED™).
Powerphone's codes are different, as are APCO's and NECI's; it all depends on which vendor your dispatch center decides to go with
--signed, a former EMD instructor for multiple vendors who had memorized more dispatch codes than any human should have