One of our technicians says adjusting the door plunger is as simple as screwing the actual plunger in or out of the hex nut. He can't be certain if you'll need to adjust this before you tighten the nut or if it will move when it's installed.
If you'd like to talk specifics please give a member of our Tundra Restaurant Supply team a call at 1-888-388-6372. We'd be happy to speak with you.