It is not possible to use decimal quantities.

To manage products sold by weight or in decimal values, you must enter integer quantities.
In each product form, register your prices in the smallest unit you are selling the product (in ounce or inch for example). When you sell the product, you will apply a multiplying factor.
ex: to sold 16 oz of product A, we type 16 times the product A (unit selling price of A = price for one ounce).
You can ask our customer service to enable prices with 3 to 5 decimals in your account (only used to calculate).

On your receipts and invoices, you can optimize how data are printed with the 'Multiple' field, you will find in each product form. It is a coefficient that will convert your prices and quantities to display them in the right unit of measure on your printing documents.
Ex: with a multiple index of 1000, if you add 65 (quantity) x 0,0432 in a sale, 0,65 x 4,32 will be printed on your receipt.

You can read barcodes printed by a scale, to scan automatically the price to invoice your customer. More information.