This reports the configured maximum byte volume this security association is allowed to carry before it must be rekeyed, as an alternative or complement to the time-based max lifetime. Admins comparing this against the live ntqVPNBytes counter can anticipate a volume-triggered rekey on high-throughput tunnels, distinct from the time-triggered rekey governed by ntqVPNMaxLifetime. On a tunnel configured with a max of 1,000,000,000 bytes, an admin watching ntqVPNBytes approach that figure would expect a rekey negotiation shortly, even if the time-based lifetime hasn't yet elapsed.