Man-section-translations-alist

Man-section-translations-alist is a variable defined in `man.el'.
Its value is

(("3C++" . "3") ("3X11" . "3") ("1-UCB" . ""))

Documentation:
Association list of bogus sections to real section numbers.
Some manpages (e.g. the Sun C++ 2.1 manpages) have section numbers in
their references which Un*x `man' does not recognize. This
association list is used to translate those sections, when found, to
the associated section number.

You can customize this variable.