[css-transitions-1]: add explanation & example for transition shorthand parsing order

css-transitions-1/Overview.bs

@@ -403,6 +403,24 @@ Value Definitions {#values}
         transition-delay.
       </p>
 
+      <p>
+        Order is also important within each transition definition for distinguishing
+				<<single-transition-property>> values from other keywords. When parsing, keywords that are
+				valid for properties other than ''transition-property'' whose values were not found earlier
+				in the shorthand must be accepted for those properties rather than for
+				''transition-property''. Furthermore, when serializing, default values of other properties
+				must be output in at least the cases necessary to distinguish a ''transition-property''
+				that could be a value of another property, and may be output in additional cases.
+      </p>
+
+			<p class="example">
+				For example, a parsed value from ''transition: ease-in ease-out'' (where
+				''transition-timing-function'' is ''transition-timing-function/ease-in'' and
+				''transition-property'' is 'ease-out') must not be serialized as
+				''transition: ease-out ease-in'' (where the ''transition-timing-function'' would be
+				''transition-timing/ease-out'' and the ''transition-property'' would be ''ease-in'').
+			</p>
+
       <p>
         If there is more than one <<single-transition>> in the shorthand,
         and any of the transitions has