Allow me to share some details about sales orders.
The sales order is a non-posting transaction that will be given to a customer before the actual sale of the items. This means when you create a sales order, the inventory items you've entered will not be deducted from the number of the available items on hand. You'll have to create an Invoice (posting transaction) to link the Quote or Sales order you've created to successfully subtract the items from the stock on hand.
In this example, I'm using Wood Parquet as the inventory item with 10,000 stock on hand and will create a quote with 1,000 items. Here's how to convert a Quote or Sales order to an Invoice.
Choose the customer you've entered when creating a quotation.
On the right pane, the quote you've just created will appear there, select Add.
Choose how much you want to put in the invoice and click Copy to Invoice.
Verify the details and select Save and close or Save and send.
Now, when you compare the stock on hand before and after creating an invoice, it shows the difference of 1,000 items. This shows that QuickBooks will automatically make changes on the number of items from the record if it is a posted transaction.