This is an event counter for how many times a packet was dropped on this interface due to a lack of switch resources, rather than a count of the individual packets themselves. Because DropEvents undercounts the true number of discarded frames -- RMON's etherStatsDropEvents semantics mean one event can correspond to many lost packets -- even a small non-zero value for this row in the rolling short-interval history table on this port is a stronger red flag than the same-sized bump in a plain packet counter would be. For example, this historical short-interval bin showing 3 drop events alongside a rising InDiscards count on the same port points at sustained buffer exhaustion on this interface, not a one-off blip.