Do you have any additional references for Connolly surfaces other than what is in the manual?
The surface area and volume calculations are performed with Michael Connolly's program for computing molecular surface areas and volume (M.L. Connolly. The Molecular Surface Package. J. Mol. Graphics 1993, 11).
For the latest information about the Connolly programs and definitions of the area and volume properties, see the following web site: http://www.best.com/~connolly/