This is a text timestamp recording exactly when one specific, already-completed 15-minute collection interval, retained in a rolling history buffer so a series of past intervals can be graphed began collecting its bytes and frames of broadcast, Layer-2 multicast, or unknown-unicast traffic that exceeded this port's flood/storm-control threshold and were dropped. On this element it is the anchor you need before trusting any of the accompanying flood-containment drop counters reported alongside it in this same bin, since without it you cannot tell whether a given count covers a completed 15-minute window (for example 14:30-14:45) or some other span entirely. For example, a start time of 2026-08-06 09:15 on this History bin tells you every flood-containment drop counter reported with it only reflects activity from that moment forward, not anything that happened earlier.