Opposed piston engine

[NSXType-R]

Forgive a slightly OT but the kinda-sorta similar 1953-on Tillings Stevens TS3 aka Commer Knocker engines sound ace

Hillman Car Club of South Australia – Commer TS3 Two Stroke Diesel Engine

YouTube - 1956 Commer C7 MkIII TS3 2-stroke

Even better sonics from this behemoth

YouTube - leyland l60 6 cylinder 12 piston engine (monster)

How come it's a 6 cylinder 12 piston engine...?

Either it's a 6 cylinder or a 12 cylinder. How can it be both?