How port use auditor calculates stats
PortUseAuditor is usually run on per building basis.
get all access devices associated with the "ns" building (eg. cssc)
iterate over devices
check to see if there is NetWatch activity on port within specified timeframe. (max 1yr limited by netwatch data retention) if so, mark active.
iterate over all access devices
operate on only ^s* devices
get current port status for device via snmp
iterate over ports
if no netwatch data, but link is up, mark as active
summary: ports on access devices with either netwatch data in the specified timeframe, or link up is counted as "in use"