Here use the button + CREATE PORTION to add servings to be sold later. Each serving is defined by its proportional size definition and its proportional price ratio to the defined size. You can also manage the servings in Dotypos Cloud.
If you define the servings there, you can use them for each created products. When a product is sold in more servings, open it in Item management and then in the list Portion activate the servings to be used for the product sale from the list of created servings. Then save the product.
Once you charge the product, you have to open the charged product preferences to select the serving being sold, in the item Portion click on the selected serving and confirm it with the button SET.