If you are in the Selection view, you can use the selection bars to decide what part of the 3D graph you want to display in the 2D graph.
The selection bars are the bars of text located below the 3D graph portion of the Selection view. The text in these bars lists either the names of rows or the names of columns in the 3D graph. The topmost bar gives the title for the rows (or columns) as a set. Compare the text in the selection bars with the labels in the 3D graph portion of the view.
The floor of the 3D graph has side panels. To read the column-names into the selection bars, click anywhere on the side panel on the right side of the 3D graph floor. (To read in the rows, click anywhere on the left-hand side panel.)