If you select an event or interval from the list under "Choose Dataset," the graph displays a scatter plot, table (for intervals only), or histogram, depending on which tab of the Show Dataset pane is currently selected. The "Choose Dataset" menu distinguishes single-event datasets from double-event (interval) datasets by displaying [1] after the names of single event datasets, and [2] after the names of interval datasets. For example, if MPI_Finalize_start is a single event dataset, and MPI_Send is an interval dataset, the "Choose Dataset" menu displays them:
MPI_Finalize_start[1] MPI_Send[2]