This sets the alert period, in minutes, over which this port evaluates egress buffer overflow events affecting its ABR (available bit rate) traffic class before declaring a threshold-crossing alert. ABR traffic is designed to adapt its rate to available bandwidth, so tolerating a somewhat longer alert period for this class on this specific port, compared to CBR, reflects that occasional ABR buffer overflows are a more expected part of that traffic class's normal congestion-responsive behavior. An admin might leave this at a longer default like 15 minutes on this port since ABR sources are expected to throttle themselves in response to brief congestion rather than needing immediate operator intervention.