http://www.chrislewisfs.co.uk/getattachment/manufacturers/Visonic/Powermax-Plus-user-guide/Powermax-Plus-user-guide.pdf
User guide, easy if you Google.
As for the "memory" its telling you there was an event. Press OK and it will tell you what has happened.
Set the system and then disarm it and it should clear.
Alarm, January 2012