Precision is a very important part of your meditation practice. You should be wakeful every minute. Mindfulness literally means being fully minded, so no activity permits you to take time off. Every activity during the day, such as eating a meal, is part of that mindfulness. So you'll be right on the dot. The connotation of being on the dot might be: "Be careful or somebody hiding behind the bushes might shoot at you!" But here being right on the dot just mean to be there. Every waking moment you communicate with the sights, sounds, feelings, and temperatures around you. The point is to be in contact with reality as much as you can.
Condensed from "Introduction to Practice," Talk One of the 1985 Seminary Transcripts, page one.