Those are single nozzle times rule of thumb.. every motor is different.
Example champion irons, roller cam, 3400 lb car, larger turbo 66+, fresh motor.. single nozzle should get mid 10's. Stock motor.. big turbo.. will need twins for mid 10's.
Its like this.. when the gain is on 8 with a single and air fuel is where it needs to be.. time for a dual. If your knob is on 6 on a single.. you have a ways to go.