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 to keep.
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 to keep."
:type 'natnum
:group 'backup
:group 'dired)