To add new, always use the “next available stock number” option unless you have a specific reason to manually enter one.
Note: manually creating a stock number might mess up the sequence for “Next Available Stock Number
Stock Number: This is the stock number associated with the inventory item. There are a few hidden shortcuts while this field is highlighted
Shift + 2: Change sold status. Can be toggled between sold and available
Shift + 6: Change stock number. You can re-assign the stock number for this item. Be careful not to overwrite an existing item