i sighted in the top dot @ 10yds at 10,20 yds same hole.went to 30 yds shot the top dot shoots 11/2" to 2" low.shot the middle dot @ 30 yds it shot 51/2" to 6" high now i am confused.how would you sight this in.barnett does not give any instruction on sighting in their scope.all advice is needed with a thank you.