I am not sure I understood the request.

On emacs built from emacs-25 branch (could not verify the same on 24.5), by
doing,

C-h i g (emacs) Backup Names

I get a very good explanation of how the backup files are named.

=====

When Emacs makes a backup file, its name is normally constructed by
appending ‘~’ to the file name being edited; thus, the backup file for
‘eval.c’ would be ‘eval.c~’.

   If access control stops Emacs from writing backup files under the
usual names, it writes the backup file as ‘~/.emacs.d/%backup%~’.  Only
one such file can exist, so only the most recently made such backup is
available.

   Emacs can also make "numbered backup files".  Numbered backup file
names contain ‘.~’, the number, and another ‘~’ after the original file
name.  Thus, the backup files of ‘eval.c’ would be called ‘eval.c.~1~’,
‘eval.c.~2~’, and so on, all the way through names like ‘eval.c.~259~’
and beyond.

[snip]
=====

Should this bug be closed?

--
Kaushal Modi