select Administration > Settings to open the vCenter Server Settings dialog box vCenter Server.
The statistics level must be less than or equal to the statistics level set for the preceeding statistics interval. This is a vCenter Server dependency.
e.g. if you set statistics level 2 at day interval, you cannot set statistics interval of 3 at week, month or year interval, you can at the max set 2 or 1 at other levels, you cannot do so and error will appear as shown below
5. (Optional) In the Database Size section, estimate the effect of the statistics settings on the database.
a. Enter the number of Physical Hosts.
b. Enter the number of Virtual Machines. The estimated space required and number of database rows required are calculated and displayed.
c. If necessary, make changes to your statistics collection settings.
Enabling a statistics interval increases the number of statistics stored in the vCenter Server database. Disabling a statistics interval disables all subsequent intervals and decreases the number of statistics stored in the vCenter Server database.