Clamping window and what the three voltage specs mean
The 1.5SMC68A-E3/9AT: The reverse standoff of 58.1 V typ sets the continuous working voltage the protected rail can sit at without the TVS conducting — above that the device begins to avalanche and clamp the transient before the downstream circuitry sees damage. Breakdown sits at 64.6 V minimum, so the clamping window between 58.1 V standoff and the 92 V maximum clamping voltage at 16.3 A peak pulse gives roughly a 28 V headroom band before the diode reaches its peak clamping ceiling.