That's the density range of your process. Now, either by densitometer or
by examining negative thru a small hole in an opaque card on a light
table, and comparing to steps on the 21 step film strip similarly seen
through hole in opaque card, match the negative to the print. That is,
make a negative with shadow density to match the bottom step, highlight
density to match the top step.
(This is explained further in the a------.)
Judy