For those of you without direct artillary experience let me explain, to help you understand the humor.
Artillary talk on the radio is precise and designed to prevent mistakes, hence, everything is repeated by the receiving person echoing what the transmitting person said, for example:
18 this is 24, adjust fire, over
24 this is 18, adjust fire, out.
(Over meaning: I am expecting a reply; Out meaning: I am not expecting a reply.)
BUT THE WORD 'REPEAT' has a special meaning.
The communication: REPEAT, over; REPEAT, out means to fire the exact # of rounds by the battery again!
So the casual use of 'REPEAT' on the radio is verboten.