This is a bitmap-style field indicating which of this interface's transmit statistics currently exceed their configured alerting thresholds. Rather than an admin having to compare every single counter on this object against its threshold policy, this one field tells them at a glance exactly which metric (say, total bytes vs. broadcast rate) tripped a threshold, cutting straight to the relevant fault. A thresholded value flagging only the broadcast-packet counters, while byte and unicast counters remain clear, tells an admin the issue is specifically Layer-2 broadcast volume, not overall link saturation.