In example 3-1 is has:
(20)       <wsen:Expires> PT10M </wsen:Expires>
in the Enumerate request.  After the example it then says:
The wsen:Expires element on line (20) indicates that the consumer would like an enumeration context that will be good for at least 10 minutes

which isn't true.  To get the "at least 10 minutes" we need to add a @min
attribute.

proposal:
change (20) to be:
(20)       <wsen:Expires min="PT10M"> PT10M </wsen:Expires>