How do you use a room code to track bookings?

The ad asks for a word when people book, for example the name of that week’s dish, and on the floor you note who said it. That shows which tables came from that ad and not from the street. Choose a short word the shift can ask for without explaining the campaign. The code changes every day and nobody on the floor asks for it. The word in the ad and the list of bookings that said it that week.