Just remember that it is a "shot opportunity" for most weapons other than large arty or ATGM.
A snipers shot opportunity can kill 2 men, as can a single survivor crewman's "pistol shot".
SAA ammo loads are therefore "shot opportunities" and could be a couple of shots, or a short burst. There is no 1 to 1 relation between them and actual rounds carried.
As to Z fire, I hardly ever fire it myself, since you go through ammo really quickly with it and then really only from MG units onto areas I know are lousy with enemy infantry. Never "on spec" - mortars are for that purpose.
I never do the USA army "recce by fire" either, as the expenditure of fire is IMHO too much for the results obtained.
As posters have said, it is something that can be agreed beforehand as to what is "sensible". Myself, I would love an opponent who is going to blaze away like that as it gives my arty observers a nice big hint as to where some landscape gardening should be done
!.
Cheers
Andy