What is lever throw and cable slack?
Lever throw is how much the lever moves in total.

Cable slack is how slack the cable is, ie. how much you have to pull before the brake pads start moving.

Park Tool says:


  Squeeze lever to test caliper brake. Adjust lever modulation setting by moving pads inward or outward from rotor by using both pad-adjusting knobs. To maintain the 2:1 ratio, turn the fixed pad-adjusting knob twice as many clicks as the moving pad-adjusting knob. For example, if a looser modulation is desired, turn the inner pad-adjusting knob counter-clockwise 4 clicks and the outer pad adjusting knob counterclockwise only 2 clicks.


The throw will be controlled by the total gap between pads and disc. For a short throw, a small gap, pads screwed a long way in, for a longer throw pads further apart, pads screwed out.