If you are selling liquid products, you can display your products on the register in two ways.
Selling by Weight
You can choose to sell your liquid products per weight. Set your item to be "Sold by Weight" on the Add Item or Edit Item screen. Make sure to indicate the unit of measure of your item (ex. Oil 1L). Set your item's price.
On the "Register" screen, select the item and a pop up will appear for you to input the desired quantity. If a customer comes to buy only 500mL of your item, input "0.5" on the field.
On the ticket at the right side of the register, the price you have set for the item will be multiplied by the quantity you have input.
Selling by Item Options
If you are selling products in specific volumes, you can use the "Item Options" when creating or editing an item.
Once you have created the main item and saved it, click on the "pen icon" to edit the item and add the item options.
On the bottom part of the "Edit Item" screen, you can find the "Add Options" section.
A. Label your item option. (Ex. Oil 500mL)
B. Set the price for that specific item option.
C. (Optional) Set the cost of the item option.
You can find your item's options on the bottom most part of the screen.