This is the number of sub frames into which each frame of the animation will be divided, and used to calculate dynamics. The higher the Steps, the more precise the calculation will be. This can be especially helpful when calculating fast movement with collision detection.
This setting is an additional way in which spring stiffness can be influenced. Generally speaking, the higher the value, the more stiff the springs. As a rule of thumb, values equal to the number of hair segments should be used. Anything higher would simply increase render times without having any additional effect.
If this option is active, dynamics will be calculated over the entire length of the project (Edit / Project Settings). If you want to adjust this setting manually, simply deactivate Auto and enter a start and end frame.