VII Boats were small compared with other subs. so they carried less deck gun ammo and torpedos , no more than 14 is a small number for a sub compared with others like the 22 of a IX-B/C boats.
(if they could be used in SH5, of course
)
Bigger boats also can carry more deck gun ammo. i read a book about british submarines and when are expected more gun action, they put all ammo as they can in the boat in every available place, increasing the total .