+.TP
+.B capab-num
+The transform capability number to use when advertising this
+transform. Both ends must have the same meaning (or, at least, a
+compatible transform) for each transform capability number they have
+in common. The default for serpent-eax is 9.
+.IP
+Transform capability numbers in the range 8..15 are intended for
+allocation by the implementation, and may be assigned as the default
+for new transforms in the future. Transform capability numbers in the
+range 0..7 are reserved for definition by the user.