Certainly those bolts are intended to be stops. In absence of official directions for adjusting them,  I would turn the steering gently to what looks sensible to you for "max left turn,"  back that bolt out to just touching & thus preventing further turning. Lock the lock nut.  Repeat for the right side.  At the extremes there should not be anything straining hard or binding and you should be enjoying the tightest turns feasible.   Somewhere buried in a shop manual there is probably a specification on max turning angles, etc.