A number N, between 1 and 96, which identifies the
interval for which the set of statistics is available.
The interval identified by 1 is the most recently
completed 15 minute interval, and the interval identified
by N is the interval immediately preceding the one
identified by N-1.
The minimum range of N is 1 through 4. The default range
is 1 to 32. The maximum range of N is 1 through 96.