This estimates what percentage of the trunk's configured bandwidth is currently being consumed by QoS1 traffic, the highest-priority class among the four QoS tiers this trunk tracks. An admin watches this figure to see whether the trunk's premium traffic class is nearing saturation, since that would mean any new premium circuit could be blocked or degraded before lower-priority classes even feel the pressure. For example, a reading of 95% on lportTrkUtilQoS1 warns the admin that priority traffic alone is nearly filling the trunk, and the trunk's total bandwidth or QoS1 allocation should be reviewed before adding more premium circuits.