Update Doc/using/cmdline.rst

Co-authored-by: Adam Turner <[email protected]>

Author: noahbkim

Doc/using/cmdline.rst

@@ -547,7 +547,9 @@ Miscellaneous options
      .. versionadded:: 3.7
 
      .. versionchanged:: next
-         Added ``-X importtime=2`` to also trace imports of loaded modules.
+
+         Added ``-X importtime=2`` to also trace imports of loaded modules,
+         and reserved values other than ``1`` and ``2`` for future use.
 
    * ``-X dev``: enable :ref:`Python Development Mode <devmode>`, introducing
      additional runtime checks that are too expensive to be enabled by