You can use Stock Adjustments. to create ad-hoc changes to your stock level at a location. This can be a positive or a negative adjustment. You can use adjustments for use cases like Wastage, Damaged or to correct a data entry error.
Adjustment Types
Every adjustment has a Adjustment Type linked to it. You can create your own types if required. To manage adjustment types go to Company Admin > Settings > Inventory
Create a Stock Adjustment
You can find the stock adjustment option either in the Stock List or in Stock Details. To find it in Stock List, first search for the product you want in Inventory > Stocks, and then click "Adjust Stock" in the overflow menu.
You will see the Stock Adjustment form now. You can select an Adjustment Type and enter the adjustment count. For example if you want to decrease your stock by 1 unit, enter -1 as the quantity. To increase it enter a positive value. Add a reason for Adjustment and click "Create Adjustment" to finalize your stock adjustment.