I was wondering the same thing and it seems these numbers were automatically added by the NeXT editor [1] (which also explains the special NEXTID tag in the hea

I was wondering the same thing and it seems these numbers were automatically added by the NeXT editor [1] (which also explains the special NEXTID tag in the header) and are not actually useful. They would make sense if the links where section titles for example. [1] http://www.the-pope.com/nextid.html