In the Cantarini pistols, each magazine holds 10 balls, and the pistol probably had enough air for one magazine.

These pistols are .40 caliber and rifled with a polygroove pattern. Each barrel is 7″ long, and the overall length is 13″. They’re numbered to match their removable butts (for filling with air) because this was before the time of interchangeable parts (ca. 1815).

https://www.pyramydair.com/blog/2007/08/cantarini-air-pistols/