Clock question

Ok this is real trivial, but hey when you spend a whole season on IR,
running clocks, these things come to you.  For a free kick. WHen the
Down and distance can't be cleared on the score board. In other words it
is lit up and It will display, whatever number you put there 0 or 10
ect. What do you want, or normally instruct, the clock operator to do?
Do you set it to read: First and ten on the forty? Or zero and zero on
the forty?