you'd have more weight if you had more liquid in the can. The can probably contains an emulsifying agent that was changed, altering how much liquid you'd need in the same volume to guarantee the aerosol effect worked.
"Is 1 fl oz the same as 1 oz?
Both fluid ounces and ounces represent a unit of measurement, but they are quite different. Fluid ounces, as the name might imply, are specifically meant to measure volume (often of liquid ingredients like water), while ounces measure weight, usually of solid ingredients like all-purpose flour."
aerosol cans typically display fluid ounces. You can google it.