I found instructions somewhere for some truck (Ford F150???):
Turn bolt in until stop, then turn it back 1/4 or 1/2 turn?
Don't remember.
(This is not instructions, it is a question)
OK, I just drove my XJ, 1/4 was not enough, I did 1/2 more, so now it is 3/4 turn.

 

Here's an even better question. Why are you wanting to adjust the steering box?

 

There is free play in it.
When adjustment doesn't work anymore, it is time to replace it.

 

The correct way is to put the box on the bench and measure the torque needed to turn the input shaft through the center position. There is an inch/lb spec which you adjust the screw to attain.
Any other method can leave you with a ruined box if you overdo it.
However you can try adjusting it 1/8 to 1/4 turn clockwise, check the free play, adjust again if necessary...rinse and repeat. Stop if you feel any difficulty turning through center or the steering stops returning to center after a turn. If that happens, back it back off again. Binding on center is what does the damage.