gh-127296: Document that argparse count action starts from a non-zero default (GH-156908)

(cherry picked from commit 7a91841)

Co-authored-by: Owen Carey <37121709+owenthcarey@users.noreply.github.com>
Co-authored-by: Savannah Ostrowski <savannah@python.org>

Author: 2 people

Doc/library/argparse.rst

@@ -734,7 +734,9 @@ how the command-line arguments should be handled. The supplied actions are:
     >>> parser.parse_args(['-vvv'])
     Namespace(verbose=3)
 
-  Note, the *default* will be ``None`` unless explicitly set to *0*.
+  Unless explicitly set, the *default* will be ``None``. If the default
+  value is a non-zero number, the count starts from that number rather
+  than from zero.
 
 * ``'help'`` - This prints a complete help message for all the options in the
   current parser and then exits. By default a help action is automatically