minor grammar fix

Author: karenetheridge

jsonschema-validation.xml

@@ -284,7 +284,7 @@
 
                 <section title="exclusiveMaximum">
                     <t>
-                        The value of "exclusiveMaximum" MUST be number, representing an exclusive upper
+                        The value of "exclusiveMaximum" MUST be a number, representing an exclusive upper
                         limit for a numeric instance.
                     </t>
                     <t>
@@ -306,7 +306,7 @@
 
                 <section title="exclusiveMinimum">
                     <t>
-                        The value of "exclusiveMinimum" MUST be number, representing an exclusive lower
+                        The value of "exclusiveMinimum" MUST be a number, representing an exclusive lower
                         limit for a numeric instance.
                     </t>
                     <t>