Using a kitchen food scale, I could see that approx 1 oz. of propane had been used. The psig pressure readings given for the meter readings above, mean pressure in pounds per square inch as compared to atmospheric pressure. Pressure readings sometimes are given as psia. Thus, the difference between a reading listed as psig and one listed as psia would be roughly 14 to 15 psi. The psia reading would be higher because it includes atmospheric pressure.
Propane is compressed by the compressor into the hot side or high pressure side tubing.
The propane, like any gas tends to get hot. If the tubing is kept cool, the high pressure propane will condense under the pressure into a liquid. This tubing full of room temperature liquid is now the same thing as the cannister full of propane. Any time a liquid vaporizes, it tends to absorb heat and make things, that it comes in contact with, very cold. The vapor finally finds its way to the input side of the pump where it is compressed again.