Summary Trend intervals in vCOPS

Hi All,

If you see the default settings of vCops  -> summary trend intervals = Daily

                                               vCops  -> Non-Trend Views

                                             Interval to use - Daily

                                            Number of Intervals to use - 30 Intervals

What exactly it means.. if the reports are generated every 30 Days?? These is required for Oversized and Undersized Vm's

Below is the screenshot of the settings.