Data is graphed in the sensor windows on X-Y axes. In the default layout, the X-axis represents time and the Y-axis represents data.
By default, data for Gyro, Heave, Pitch and Roll sensors are displayed.

Each sensor window contains two graphs. The graph in the top of the window shows time series data for the sensor. The graph at the bottom of the window is a down-sampled view of the time series for the entire selected line.
This overview graph can be useful for locating data outliers and gaps. It can be displayed or hidden for each individual graph.
To hide the overview graph: