reason: ninety-nine, which means one is missing from one hundred. remove the top one and it is white.
others: people usually call 99-year-old Bai Shou, 88-year-old Mi Shou (with eight inverted characters above the "ten" and eight below, which is "rice"), 98-year-old Miscellaneous Shou (with nine above and eight below the "ten"), and China's word game.