This is a text timestamp recording the actual moment one specific, already-completed 24-hour (daily) bin, kept for day-over-day comparison stopped 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, since this bin has already closed. Paired with the bin's start time it lets you compute the exact wall-clock span the neighboring flood-containment drop counters actually cover, which matters here because a Hist24H bin cut short mid-way (say, by a card reset) would otherwise look identical to one that ran its full 24-hour length. For instance, a Hist24H bin whose end time is only a few minutes after its start time, instead of the full 24-hour apart, tells you the flood-containment drop totals reported with it cover a truncated window and will read lower than a normal bin purely because of that, not because traffic was actually light.