Permit system info unfortunately cant' expressly explain it that way, because the reg is written in such a way that the date is the date.  I think the rangers know it is a dumb system, so administer it reasonably.  Better system would be to simply allocate exits to a limited number of entry permits, without even naming an exit date, as in the Yos Donohue deal.  Effect on trail use would be exactly the same without the anxiety.