長いls出力で大文字Sの意味

私のものからman 1 ls：

各フィールドには3つの文字位置があります。

...

  3.   The first of the following that applies:

       S     If in the owner permissions, the file is not exe-
             cutable and set-user-ID mode is set.  If in the
             group permissions, the file is not executable and
             set-group-ID mode is set.

       s     If in the owner permissions, the file is exe-
             cutable and set-user-ID mode is set.  If in the
             group permissions, the file is executable and set-
             group-ID mode is set.

       x     The file is executable or the directory is search-
             able.

       -     The file is neither readable, writable, exe-
             cutable, nor set-user-ID nor set-group-ID mode,
             nor sticky.  (See below.)

もともと、

S == setuid/setgid && not executable
s == setuid/setgid && executable
x == not setuid/setgid && executable
- == not setuid/setgid && not executable