This counter reports the total bytes of broadcast traffic on this port that exceeded the configured flood/storm-control threshold and were therefore dropped rather than forwarded, during the current, still-filling 15-minute window. A nonzero or rising value building up right now in the still-accumulating current interval is the storm-control mechanism actively protecting the rest of the network from a broadcast flood, so it directly signals a burst of ARP or DHCP broadcast traffic, such as from a rogue DHCP server or a bridging loop is happening on this specific port, not a general congestion issue elsewhere in the network. For example, a burst of ARP or DHCP broadcast traffic, such as from a rogue DHCP server or a bridging loop could push this counter from near zero up to several megabytes within the still-accumulating current interval before dropping back to zero once the source is disconnected -- exactly the transient event this counter exists to catch.