The number of previous far end days for
which data was collected. The value will be
30 unless the interface was brought online within
the last 30 days, in which case the value will be
the number of complete 24 hour far end days
since the interface has been online. In
the case where the agent is a proxy, it is
possible that some intervals are unavailable. In
this case, this interval is the maximum interval
number for which data is available.