This sets the minimum percentage of bandwidth, with 0% as the lowest possible setting, that this QoS profile's queue is guaranteed by the switch, meaning the switch is obligated to provide at least this much bandwidth to the queue rather than treating it as merely a suggestion. An admin sets this to guarantee a baseline throughput for a critical traffic class, ensuring it isn't starved even under heavy overall congestion. For example, setting this to 20% for a voice traffic profile guarantees that queue always gets at least a fifth of link bandwidth, even when data traffic on other queues is saturating the rest of the link.