It is called minimum stay requirement due to heavily booked on certain days. You should call PC to ask whether you can book into the dates you desired. Otherwise you have to do a @EARLY DEPARTURE@ or @Late Arrival@. Both case you will loose your points because the reservation has to be made in one block rather than a per night basis. but you never know that you might be lucky to get your points back but some hotel will impose an Eary departure fee. And another risk is if you did not show up for your reservation you will be charged for no-show and result in whole reservation cancelled.

So the best is to call PC to ask whether would be nice to book you in the date you desire or just pay for the stay.