It's not fully clear exactly what you are doing here, but to provide a general answer that may give you the info you need to make this work...
You can most easily compute totals for groups of records in two ways:
1) the current found set--this is what you have working now.
2) A set of related records--which can be all the records in the table and can even include the same records from the same data source table as those in your current found set. A "self join" like this is one possibility:
YourTable::anyfield x YourTable 2::anyfield
You use the button with two green plus signs to duplicate the table occurrene box in Manage | Database | Relationshps to create "yourTable 2" and you then drag from any field in YourTable to any field in YourTable 2, then double click the relationship line where you change the = to x to get a cartesian join operator.
With that set up, aggregrate functions like sum, count, average can be set up as Sum ( YourTable 2::Numberfield ) to get totals for the set of related records--every record in your table in this case. You can also refer to summary fields defined in your table, but from the YourTable 2 table occurrence instead of YourTable to get a total for the complete set of records in the table.
And there are other relationships and/or filtered portals you can set up to get sub totals for all records in your table for a given category.