Fix retain labels.

This is a numeric value based on the character offset of -k from the beginning of the switches.

org_mode_samples/lesser_element/lesser_block/example/switches_with_label.org

@@ -1,3 +1,15 @@
-#+BEGIN_SRC elisp -n -r -l "((%s))"
+#+BEGIN_EXAMPLE elisp -n -r -l "((%s))"
    foo
-#+END_SRC
+#+END_EXAMPLE
+
+#+BEGIN_EXAMPLE elisp -k -n -r -l "((%s))"
+   foo
+#+END_EXAMPLE
+
+#+BEGIN_EXAMPLE elisp -k 8 -n -r -l "((%s))"
+   foo
+#+END_EXAMPLE
+
+#+BEGIN_EXAMPLE elisp -n -r -k -l "((%s))"
+   foo
+#+END_EXAMPLE