kingpin/steering axis inclination is the imaginary line formed by the tilt inward of the upper ball joint [or kingpin] from true vertical compared to the spindle's horizontal line. this is controlled by the way the spindle is made, so it is a segment that can't be changed.
it's purpose is to place the vehicle load on the road contact patch of the tire, providing better tracking and easier steering.
this only works for OEM applications, using the parts designed for the vehicle in question.
any mix and match of control arms, spindles, and wheel offsets throws this spec out the window.
a guy can math out the original setup then do the same after the parts used to see how far off or close you come to OEM, but it is hardly, if ever, done.