Transient protection for a 24 V rail
Its 25.6 V reverse standoff voltage sits just above a regulated 24 V supply, so it stays transparent during normal operation and only conducts when a surge pushes the line above its 28.5 V minimum breakdown threshold.
Clamping voltage and surge current — what they mean on the board
At the 75 A peak pulse current (8/20 µs waveform), the clamping voltage rises to 53.5 V maximum. The 28.5 V minimum breakdown gives a 2.9 V guard band above the 25.6 V standoff, which is tight enough for a 24 V rail with ±5 % regulation but leaves little margin if the rail drifts high during fault conditions.