Joke - Cryptographers

A newly appointed cryptographer attends a lunch meeting with his peers, who are going around a circle telling jokes.

One of the cryptographers shouts "12", and everyone starts laughing.

Another person shouts "34", which is received with more laughter.

The new cryptographer asks one of the people "why is everyone laughing?" to which he responds "instead of taking the time to tell the whole joke, we just assign each joke a number and instead say that number".

When it's the new cryptographer's turn, he says "-22", to which everyone bursts in laughter.

One of them shouts, "i haven't heard that one before!"