More accurate test contact related README wording

README.rst

@@ -147,11 +147,11 @@ You can override the default ``Contact`` model by setting an option on the admin
 
 .. code-block:: python
 
-    # You may want to extend the test contact
+    # You may want to redefine the test contact (used in previews) with your new ExtendedContact fields
     BIRDSONG_TEST_CONTACT = {
         'first_name': 'Wagtail',
         'last_name': 'Birdsong',
-        'email': 'birdsong@example.com',
+        'email': 'wagtail.birdsong@example.com',
         'location': 'us',
     }