If two rows are equal in value for the first rule, the next rule is used to determine the order. You can specify as many rules as required.
Column – select a column by column letter position (optionally by Name).
Sort On – select a sorting option to use, optionally check Case sensitive to order upper and lower case letters differently.
Order – select whether to sort ascending or descending order.
Add Rule – adds the selections above to the sort rules list. When multiple rules exist, they will be executed in order; if there is a tie in the first rule, the second rule is used to determine order.
Delete – remove the selected rule from the list.
Up / Down – move the selected rule up or down in the list. The rules will be run in order, so the first rule has highest priority.
This is usually done in trend reports, with the highest value in the last period, and equal values ordered by the previous period numbers.