A read-only value that reports the -off time- for a
grant burst in increments of Time Quanta (TQ) 16ns as
defined in [802.3ah] 60,64. The value returned shall be
(off time ns)/16. If this value exceeds (2^32-1) the
value (2^32-1) shall be returned.
This attribute is relevant for an OLT and an ONU.