How to increment a number counter field?

[Robert_Petitto]

Reducing a sheet cell’s value when a form is submitted

Yep! I have a version of this in my Inventory app (itemstore.glideapp.io). Set a quantity for an item, then every time a user buys an item, the quantity decreases: [ScreenFlow] Basically, set an initial quantity in the shop tab. Do a multiple relation to the SKU between shop tab and purchases tab. Rollup the count of purchases within the relation. Subtract the count from the quantity using a math column. Display the result. Hide the buy button once the inventory reaches zero.