You can keep track of items by Stores (Shops, Warehouses).
Every Store keeps its own quantity in stock. Every document's transactions are also attached to specific Store.
You can move goods between your Stores with "Transfer" document or use button with arrows besides "Quantity" field in "Edit item" screen.
In the Main Menu you can select current Store to work with or select "All stores" to see total number of items in all Stores and all documents. Reports are also generated for the currently selected Store.
You can add more stores using "Stores" item in Main Menu.
In the free version you can work with 2 stores. If you need more Stores you can buy a subscription "Multiple Stores" or "Complete Pro". Every subscription provides 7-days free trial.