In 'Settings/Users/Access Management', enable the right: 'Print summary receipts (non-itemized receipt)'.

In 'Settings/Printing/Receipt', you can configure the default title for a summary receipt.

Once the sale is validated, go to the Payment section and click the 'Non-itemized receipt' button.
Enter the quantity and, if needed, modify the default label that will be printed.
The amount on the summary receipt will be the total amount of the sale.