Sync Inventory
After updating your inventory - best practice is to sync inventory to ensure the correct quantities show in your store.
You may be required to sync your inventory to ensure the correct quantities are showing on the website.
In this example the product listing is showing as 2 units available.
However, when you view the quantities within the product listing in your store each variant only has 1 in stock.
Within the product listing select More Action and then Sync Inventory. The system will update. Please allow sufficient time for the sync to occur.
Check the stock level again in the front end of your store to confirm the correct quantities are now available.