...
If the Enable Additional Price Factor option is selected on the Administration > Settings > Sales form, you can select a particular factor defining which price list must be used. The Price column is filled in automatically if prices are available from the appropriate price list (see Price Lists Item Pricing). You can enter the prices manually if you have appropriate access rights.
The Discount,% and Discount (or Discount Price) columns are available if the Enable discounts and markups in sales documents option is selected on the Administration > Settings > Sales form. Use these columns to specify the manual discount granted to the customer. The default discount can be set in the customer contract. The Auto-Discount % and Auto-Discount columns are available if the Enable Automatic Discounts and Markups option is selected on the Administration > Settings > Sales form.
The values in the Amount column are automatically calculated for each item according to the specified priceprices, quantityquantities, and discountdiscounts.
If the VAT Applied option is selected for this document on the Main tab, the VAT, % and VAT Amount columns are available. The VAT amount is calculated in the currency of the document according to the amount and VAT-related settings (which are specified on the Main tab) as follows:
...