I don't think I'd ever use that 'mal' phrasing. It would have to be "2 mal ein Helles" [~one light beer, twice] for it not to sound totally off to me. But "1/2/

I don't think I'd ever use that 'mal' phrasing. It would have to be "2 mal ein Helles" [~one light beer, twice] for it not to sound totally off to me. But "1/2/3 Helle[s]/Bier/Halbe[s]" [normal plural] is what I'd say. (I'm from Franconia.)