To be safe you can go about a 1/8 to 1/4 turn at a time until it feels tighter. After a few of these turns it stops making any differance. You'll also get to a point where the adjustment bolt will turn stiffer and that means you gone a little to far.
Adjusting a steering box is just a band-aid. You'll eventually need to replace the box.
2000 F-250, SC, SB, 4X4, Lariat, 6.8 V10, Auto, 3.73, Ford Racing headers, SCT X3 tunes by 5 Star Tuning