12 oz beverage cans have 375 mL of total volume and the label claim is for 355 mL. The can manufacturers designed this extra 20 mL in the can for headspace above the liquid. Beverage cans should have 3-5% headspace for expansion so cans do not buckle. If your mobile canner is capping on liquid they don't understand pressurized packaging and they are putting you at risk for buckling or exploding cans when the liquid in the sealed can expands at elevated temperatures or when the carbon dioxide comes out of solution and has no where to go. The link below from Brewing Industry Guide discusses the importance of headspace in the can.
https://brewingindustryguide.com/the-science-of-exploding-beer-cans/
We selected our Codi Canning line since it makes it extremely easy to insure we have headspace in our cans. By controlling our pressure differential and the throttle we can get very specific control of our product fill weights to make sure we have the right amount of headspace. Then we make sure to cap on foam to keep the total packaged oxygen in the can nice and low.
Call WilCraft Can to find out more about how we are truly a different mobile canner.