For new item, users can specify the stock quantity when creating the item at admin section:

1. Select Admin on the top menu

2. Select Inventory -> Inventory Item on the left menu

3. Click New button on the right page to create a new item

4. Fill in the stock quantity

For existing item, the stock quantity changes when there are new delivery:

1. Select Inventory on the top menu

2. Select Delivery tab

3. Press "New Delivery" to create new delivery

4. Enter the inventory item delivered, with the quantity, lot number and expiry date

5. Press "Create" and the stock quantity change is applied