[Steeveedee]

The hose and can are pressurized to whatever the low side of the AC was at when you disconnected the hose. So, a fair amount, really. That's why we are supposed to recycle the cans- so that left-over amount in the can doesn't go into the atmosphere. You could weigh it before and after to get an idea, but it's only going to be a few grams. Not a big deal, but just consider how many thousands (millions?) of cans are out there.