Of course you know the answer. Depends on how much beer. 10.4 Volumes/gallon. Assuming 5 gallons 2.1 Volumes.
But I didn't need to know the pressure or temp to know that. Similar to say volumetric flow of gas given in SCFM, not really a mass but in terms of your variable set can be treated as a "mass unit" not a "volume unit." Maybe referring to design variables that way is industry specific. If someone wants me to design a condenser and gives me volumetric flows I'm going to approach it one way; if someone gives me SCFM, mass flows, partial pressures, molar ratios, ect. I'm going to approach it another.
In the context of this thread I was stating that a small headspace at a higher pressure may absorb quicker than a large headspace at lower pressure because there is less mass even the the volume at lower pressure is larger. And with the name "Volumes" it's easy to confuse and think that Volumes is a volume CO2 to volume beer ratio that is dependent on the pressure/temp that you carbonate at, not that the pressure/temp is a saturation point. I think confusion over this is why there are so many variations of burst carbonation around.