Then you create a second smart lighting rule to turn the light on when the door opens during the desired timeframe.
That should be all you need.
If you want it to only turn off after 30 minutes if it was turned on because of the door opening, but to stay on if it was turned on in some other fashion, see the how to article in the community – created wiki on creating a virtual timer:
I created two SmartApps. The first works if my Arlo front of the house camera gets a motion trigger after 8:30pm. That forces the light to go on. A second smartapp only allows the light to stay on an hour, well after the the dog sitter should have left for the evening. I’ll test it all tonight on myself.