Hi DK007,
For the spam notification in Exchange Online Protection, you can specify a value between 1 and 15 days time period. First of all, you need to enable the end-user spam notifications. And then set the time period.
Please click on the link below and follow the steps in there to configure end-user spam notifications.
http://technet.microsoft.com/en-us/library/dn296367%28v=exchg.150%29.aspx
You also can refer to the link below about the blog of Manage spam notifications with Exchange Online Protection.
http://blogs.office.com/2013/09/19/manage-spam-notifications-with-exchange-online-protection/
Thanks,
Yang Yu