The X-base (time base) settings are important for plotting, as they allow you to change the range of data displayed. Sometimes you have an extremely long file and you need to see what was happening during one hour in a window; other times, you may need to perform a detailed analysis and observe the process details over the span of one second.
Picture 1: time base 60 seconds – more condensed
Picture 2: time base 30 seconds – more details