recentf-show-file-shortcuts-flag

recentf-show-file-shortcuts-flag is a variable defined in `recentf.el'.
Its value is

t

Documentation:
Whether to show ``[N]'' for the Nth item up to 10.
If non-nil, `recentf-open-files' will show labels for keys that can be
used as shortcuts to open the Nth file.

You can customize this variable.