Definition: I believe that's an abbreviation for "Zero Five Sixty Three." The Hebrew term "zero five sixty three" means 10, 12, 14, or 17 in Yiddish, meaning a year. It's also used to mean "one thousand five hundred and sixty-three," which is the number of days between January 1st and February 28th (or between December 31st and January 1st).
closed bracket.
what should be said.