Payment vouchers are vouchers that have a fixed monetary value. They're different from concession vouchers, which are exchanged for particular concessions.
Payment voucher records represent the product customers will ask for at POS, or select on other sales channels. They don't represent individual vouchers.
If your staff had a booklet of $10 vouchers behind the counter, with 100 vouchers printed inside the booklet, you'd use the Payment voucher page to create a '$10 vouchers' record. POS operators would select that record at POS to sell vouchers in the booklet.
Configure the details of payment vouchers, such as their value and barcode details, in Cinema Manager > Maintenance > Payment vouchers. You'll also need to create an item to represent the voucher on your sales channels, and generate stock for the voucher itself.