"Here lies our dear mother,Khentcheh daughter of Zvi, died 30th of Tevet 5684" (January 7, 1924)
Obviously, either the civil or the Hebrew date is wrong.  December 8, 1923 = 30th of Kislev 5684.
I would say that the error is in the Hebrew month.  However, the only way to be sure is to reference some other document (death certificate, obituary, etc.)
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Steve Goldberg
Jerusalem, Israel
Researching:
Sagan/Shagan family from Veliuona (Velon), Lithuania
Goldberg family from Vidukle, Lithuania
Susselovitch/Zuselovitch family from Raseiniai (Rassein), Lithuania