This would be a Custom Value (location-wide data) of type = Number on which we can perform Math Operations.
Primary use case is to track maximum number of a limited product. Right now the contact can purchase a specific number of a product, but there is no limit for how many contacts can make that purchase.
For a pure digital product this might be acceptable. But there are many use cases where we would want to limit the number of purchases (limited number of people in a coaching program for example). https://youtu.be/za6Eht1WEjc