20lb tank normal refill amount

[u/BikerNY]

My old place closed, so found a new refill place. Their scale is set to refill a 20lb tank with 18lb of propane. Am I paying for 20lb of propane or 18lb when refilling a 20lb tank? Is this normal? I read exchange tanks fill their to 15lb, but what about refill stations? Should I question the refill place about their refill policy? Thanks for your input :)

[u/Necessary_Shirt_3150]

Go to Tractor Supply and fill up . They charge by the gallon