sub_total: Sum of Order Line extended_amount fields.
order_discount: Total post-tax discount on order as a positive number.
sales_tax: Total tax on order
shipping_handling: Total shipping charge for the order passed from cart. No relation to the order line shipping_surcharge field.
grand_total: sub_total + sales_tax + shipping_handling - order_discount
balance: Not used right now. Set to 0 or leave off completely.
quantity: Number/Quantity of this product ordered.
price: Cost of a single item. Does not include taxes, discounts, or shipping charges.
discount: Pre-tax Discount amounts to be applied to EACH single item as a positive number.
addl_discount: Post-tax Discount amount to be applied to the total item line as a positive number.
tax: Taxes applied to the total quantity of the total items in this line.
shipping_surcharge: Extra shipping charges that were added because of the total items in this line.
extended_amount: (price - discount) * quantity