In Store in the Magpie app, a bundle's product screen lists its parts with their stock and says how many bundles can be sold from the parts in stock. Add part adds an item the Store sells; select a part to change how many each bundle holds or to remove it.
Bundle parts in the Magpie app
A bundle's product screen in the Magpie app lists its parts and how many bundles can be sold, and adds, changes and removes parts.