The configuration index consists of two segments separated by a hyphen. The first segment consists of two digits which are the priority numbers of the ligands on the five, six or sevenfold rotation axis. The lowest numerical value is cited first.
The second segment consists of 5, 6 or 7 digits respectively. The lowest priority number is the first digit followed by the digits of the other atoms in the plane. The clockwise and anticlockwise sequences are compared and the one that yields the lowest numerical sequence is chosen.