Does a 20lb propane bottle hold 20 lbs of propane? Is that 20 lbs just a generic term? I weighed an empty 20 lb bottle on an electronic scale at 23.2 lbs. It weighed 38.0 lbs after being filled. That accounts for 14.8 lbs loaded into the bottle. I had the bottle filled, not exchanged. Maybe they are selling it in gallons, and just terming it lbs. Anything I am not considering?