NMOS gives the number of MOs to be read in. This prevents shredding the plot paper near nuclear cusps. The default is Bohrs. 5D specifies the pure basis of true basis-functions. This is a debug option, and chews up lots of paper.
SIZE is a scale factor for the plot.
The default is full size, 0.5 would give half that size. These are the Cartesian coordinates of the atom denoted by the string . The coordinates of atom are taken as the origin of plotting plane. Px points from towards . Py lies in the plane defined by the third atom , and is automatically made orthogonal to Px.