As other reviewers, I was disappointed to find that there seemed to be no exit delay when arming the Delay function. However, I couldn't believe that this function had been missed out so I fiddled about a bit trying different key presses etc.
Eventually I stumbled on the solution, the Delay function MUST be armed when the door is open (or sensors well apart). When it is armed in this way there appears to be an unlimited time to exit and the arming is completed when the door is closed. When the door is reopened you then, of course, have the documented 10 seconds to disarm the unit.
I almost bought another make that listed the exit delay in the specification so this little bit of experimentation has saved me a few bob!
It's a shame that this is not better explained in the user guide as the unit is good value for what it is.