This is the archived peak broadcast-packet delta recorded at the time of this historical sample. This stored peak is what an admin uses to build a historical record of this interface's worst broadcast bursts over time, useful for justifying a policy change (like tightening a storm-control threshold) with concrete past evidence. A series of historical deltaMax rows all around 500 followed by one at 50,000 would document the exact archived sample where a one-time storm event occurred on this interface.