Coding, StdPrs_ToolTriangulatedShape::Normal() - range of "for" not correspond to the NCollection index which run in "for"

void StdPrs_ToolTriangulatedShape::Normal (const TopoDS_Face& theFace,
                                           Poly_Connect& thePolyConnect,
                                           TColgp_Array1OfDir& theNormals)
{
  const Handle(Poly_Triangulation)& aPolyTri = thePolyConnect.Triangulation();
  if (!aPolyTri->HasNormals())
  {
    ComputeNormals (theFace, aPolyTri, thePolyConnect);
  }

  gp_Vec3f aNormal;
** for (Standard_Integer aNodeIter = 1; aNodeIter <= aPolyTri->NbNodes(); ++aNodeIter)
  {
** aPolyTri->Normal (aNodeIter, aNormal);
    theNormals.ChangeValue (aNodeIter).SetCoord (aNormal.x(), aNormal.y(), aNormal.z());
  }

  if (theFace.Orientation() == TopAbs_REVERSED)
  {
** for (Standard_Integer aNodeIter = 1; aNodeIter <= aPolyTri->NbNodes(); ++aNodeIter)
    {
** theNormals.ChangeValue (aNodeIter).Reverse();
    }
  }
}

code crash at line start with *
thr "for" take range between (1,aPolyTri->NbNodes())
but inside "for", theNormals,ChangeValue take range between (0,aPolyTri->NbNodes()-1)