You can access the configuration settings of the Two Dimensional Widget by clicking on the three dots in the top right corner of the widget and selecting Settings or by clicking on the blue arrow at the right side of the widget.
The Two Dimensional Widget saves your configured settings permanently. Your configuration persists even if you change items or groupings on the board. You can change the settings of your widget at any time.
After successfully configuring the widget, an info text gets shown below the table, detailing which numerical column gets summed up by which categorical columns on the x- and y-axis.