A number (normally between 1 and 96 to cover a 24 hour
period) 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 through 32. The
maximum value of N is 96.