A stock number is only useful if you can see how it got there. Every movement is now recorded, and the overview adds up to what is on the shelf.
In, Out and Adjusted
Stock in, stock out and manual adjustments are separate recorded actions, each with a reason, so the balance is explainable.
Per Location
Stock is tracked per inventory location, so a multi-site business knows what is where rather than what it has in total.
The History Behind the Number
Every movement is listed, so a discrepancy is traced to the entry that caused it instead of being written off.