Update jsonschema-validation.xml

Co-authored-by: Ben Hutton <relequestual@gmail.com>

Author: jdesrosiers

jsonschema-validation.xml

@@ -500,8 +500,9 @@
                     </t>
                     <t>
                         An object instance is valid against this keyword if every property name
-                        declared in "properties" is the name of a property in the instance, with
-                        the exception of the property names that appear in this keyword's array.
+                        declared in "properties" within the same schema object is the name of
+                        a property in the instance, with the exception of the property names
+                        that appear in this keyword's array.
                     </t>
                 </section>