Using Statistics in Financial Tables
Statistics rows can be used in conjunction with mathematical columns to allow you to perform quite complex calculations. They can also be used to print values which are excluded from totals.
Statistics rows are often not printed, but used for calculation in reports. A statistic row can collect information which is used later. For example, you might have a Statistic Row type that totals income accounts. This total can then be used by a table column to calculate ratio to sales.
See Sample Gross Profit Report Using Statistics.