Depends on which end you want to (un)twist and which way your string is twisted.

If from the bottom of the bow the string twists upward and to the right and you are going to twist this end then you need to untwist the string 1/2 turn. If you were going to twist the other end then you would want to add a half twist.

Of course if you shoot a loop then I would simply twist the loop slightly to the left so that it pulls the peep straight at full draw.