A multi balance report is a kind of periodic report, where the amounts correspond to balance changes or ending balances in a given period. It has:
a list of each column's period (date span)
a list of rows, each containing:
the full account name, display name, and display depth
A list of amounts, one for each column.
the total of the row's amounts for a periodic report
the average of the row's amounts
the column totals, and the overall grand total (or zero for cumulative/historical reports) and grand average.