Platonic Icosahedron Truncation

Does anyone know what the "Truncation" parameter in Platonic Polyhedra is?  Common usage of the term, for example, takes an icosahedron to a soccer ball by truncating the vertices.  But the Lunchbox "Truncate" does not do this.  If I add a number slider the geometry immediately changes, evidently by changing the dihedral angle of the edges.  And I could only get back to the equilateral state of the original by disconnecting the slider.  (OK, I'm sure there is some way, but it was not transparent to me.)  Maybe call this parameter: "Dihedral" and add a real "Truncate."

Anyone else work with this command?