An electrical device such as this requires reverse leakage current of 45nA @ 21V.During operation, the maximum voltage - Zener (Nom) is reduced to 30V volts.
BZX585B30 RKG Features
reverse leakage current of 45nA @ 21V 45nA @ 21V is the maximum voltage (Tol)
BZX585B30 RKG Applications
There are a lot of Taiwan Semiconductor Corporation BZX585B30 RKG applications of zener single diodes.