To control how data is displayed in a combination graph, please go to the "Property/Plot Area" tab of the Report Editor. At the bottom of the tab, there is a "Series Options" setting. The "Color" column maps onto the different series shown in the graph. The "Graph Type" column specifies how the series should be displayed (bar, area or line).
For the combination graph, you may want to see the actual data intended for the report in the example graph shown in the right of the editor tabs. To do this:-
1/ Select the connection to be used to run the report query in the drop down at the top right of the editor.
2/ Go to the "Property/Data" tab and select the "Use Live Data" check box.
I hope this helps you with using the combination graph.
SQLDev Development Team.