System Reporter chart tooltips appear to be incorrect

Symptom

Time-and-value points are not properly shown in chart tooltips when more data points are returned from a storage system than are plotted in a chart.

For example, consider two data points returned from a storage system, such as (09:49:58, 230.05) and (09:50:03, 289.88). When the chart shows many data points and a mouse pointer is moved near this time period, the tooltip shows (09:50:00, 238.7933333333).

Cause

System Reporter time-interval reports use data point grouping. Data point grouping replaces a sequence of data points with one grouped point, which is plotted in the chart. The value of each grouped point is calculated from the original values of the returned data points.

Action
To see the actual data point values, you can zoom into the chart. Learn more: Zooming into charts.