About Chart Series Minimums

The minimum is the smallest value of data to be displayed on an axis. You can manipulate the minimum value to focus on data when it falls in the middle or toward the top of the Y-axis.

For example, a chart whose Y1 axis is set to Auto may appear as:

Perhaps you want to examine the peak usage for this day more closely. Set the Y1-axis minimum to a larger value. The chart is redrawn and effectively "zooms in" on the peak usage data.