The total statement evaluates the difference between the original value and the new value of the expression when a field is changed, and adds it to the current value of the field containing the total statement. The total statement should only be used in Copy/Calculate formulas.
You can use the total statement to total an expression on a repeating form, for example, a subtotal field containing total (amount). The subtotal field sums the changes to the amount field on each record processed on that repeating form. On the next form, normally you would have a field with a += detail.subtotal Copy/Calculate formula that accumulates the changes.
total (amount * taxable)