What are the torque settings used for and how do I adjust them?

The adjustable torque clutch allows you to drive different types of screws into different materials by rotating the adjusting ring to one of 24 settings: 1-4 for small screws, 5-8 for soft materials, 9-12 for soft and hard materials, 13-16 for hard wood, 17-20 for large screws, and 21+ for heavy drilling. (Page 12)