Thanks to all for your informative and interesting responses. I printed the
diagram (thank you Mike Collum) and added it to my Vanagon service file.

The reason I asked is that my usual propane filling attendant, said the tank
was still full when I expected it to be down by half after 4-5 days of
camping (running the Dometic full time and light cooking/coffee-making). Now
that I know more about the AS valve, I wonder if the re-set button needed to
be pressed?

Also, my 2nd tank (independent from the main tank and used just for the
Propex heater) also has an AS valve. I noticed that the main valve has a
little rubber cover over the red re-set button and that my aux. tank is
missing the rubber. Thoughts?