This estimates what percentage of the trunk's configured bandwidth is currently being consumed by QoS3 traffic, a lower-priority class typically carrying bulk or less time-sensitive data. An admin watches this figure to see how much of the trunk a lower-priority application, such as batch file transfers, is consuming without necessarily threatening higher-priority classes. For example, a QoS3 utilization holding steady near 80% during nightly batch jobs, while QoS1 and QoS2 stay low, shows the trunk's off-hours load is dominated by bulk traffic as expected.