docs: improve explanation

Author: kenjis

user_guide_src/source/installation/upgrade_422.rst

@@ -26,7 +26,7 @@ Web Page Caching Bug Fix
 Others
 ======
 
-- The method ``Forge::createTable()`` no longer executes a ``CREATE TABLE IF NOT EXISTS``. If table is not found in ``$db->tableExists($table)`` then ``CREATE TABLE`` is executed.
+- The method ``Forge::createTable()`` no longer executes a ``CREATE TABLE IF NOT EXISTS``.  When `$ifNotExists` is true, if the table is not found in ``$db->tableExists($table)`` then ``CREATE TABLE`` is executed.
 - The second parameter ``$ifNotExists`` of ``Forge::_createTable()`` is deprecated. It is no longer used and will be removed in a future release.
 - When you use :php:func:`random_string` with the first parameter ``'crypto'``, now if you set the second parameter ``$len`` to an odd number, ``InvalidArgumentException`` will be thrown. Change the parameter to an even number.