Online Documentation for SQL Manager for PostgreSQL
If necessary, you can select the Column Summary... context menu item to open the Column Summary dialog which allows you to set the summary for each particular column that will be displayed in the grid footer, group header and group footer areas.
The Column list displays all columns of the dataset. Select a column and specify which information should be displayed in the grid as summary for this column:
Sum (for numeric types only)
Minimum (for numeric and date/time types only)
Maximum (for numeric and date/time types only)
Average (for numeric types only)
Use the Number format edit boxes in each group to specify the preferable format for summary info representation.