Variable: dired-kept-versions
dired-kept-versions is a customizable variable defined in files.el.gz.
Value
2
Documentation
When cleaning directory, number of versions of numbered backups to keep.
See version-control, kept-old-versions and kept-new-versions for
more about keeping and deleting old versioned (a.k.a. "numbered")
backup files.
Probably introduced at or before Emacs version 17.
Source Code
;; Defined in /usr/src/emacs/lisp/files.el.gz
(defcustom dired-kept-versions 2
"When cleaning directory, number of versions of numbered backups to keep.
See `version-control', `kept-old-versions' and `kept-new-versions' for
more about keeping and deleting old versioned (a.k.a. \"numbered\")
backup files."
:type 'natnum
:group 'backup
:group 'dired)