HP 220240 - Manual (Page 62)

3. Rotate the print density adjustment dial so that the desired density
number is opposite the index triangle.
Numbers on the dial are displayed in increments of 2.
Number 1 is the darkest setting; number 9 is the lightest setting.
Although the printer is shipped with the dial set to number 5, you
can typically obtain acceptable print quality, prolong the cartridge
life, and reduce toner consumption by setting the dial to 7.
MLO-004849 (Figure 2-34; 16 picas)
Operating Information 2–35