Depends, further into the tiller process,it will stick out further, as the arc increases, (or as the radius of the circle decreases).
It probably protrudes anything from1 mm to maybe two or three mm.
I always start with it just protruding, pull the bow to the desired point, run the gizmo, and if it leaves no mark, twist the pencil out a fraction, and try again!
Until I start getting marks on the limb, if I lose the marks, then the pencil is not protruding enough.