These graphs show the values of simulation variables over time. The display you see here is the one for Semi-Closed or Closed circuits; for Open circuits, the top two graphs will change to VA and CO. The X-axis is shared by all three graphs. Its scale is set by the view size drop-down control in the lower left (shown with '30 minutes' selected in the illustration). The interval shown on the shared X-axis is determined by the scrollbar if the simulated duration exceeds the view size.