fmOrderCalculations - Order Calculations Form
This section is for you to change shipping method and cost, provide or change the discount and see how it affects order totals.
The most interesting option of this section is 'Calculation Settings' . When you click on Settings Button you'll see the Order Calculations window. Here you can configure how order values will be calculated.
Formula is an arithmetical expression. It can contain two types of elements - operand and operator.
There are three hardcoded operands:
Other operands can be inserted by clicking right mouse button on formula field.
Allowed operators: + add; - subtract; / divide; * multiply. Also you can use round brackets ( )
Find more information about expressions here.
Value specified in square brackets represents default value for an operand if specified operand name was not found. As for example order total (formula above) calculated as subtotal + tax + shipping... but it should be taken into consideration that actually not every order have tax and shipping fields. If fields specified in formula are not found it will take default value.
Formula operand [ot_tax, 0.0] has default value of 0.0, [ot_tax, 15.5] and means default value of 15.5 and so on.