What does the Torah mean when it writes "Lo Yom Echad, Lo Yomayim
Ramban #1: It means 'Not just 1 one day, not just two days... rather, 30 days!'
Ramban #2: It means 'You won't eat it for one day, or for two days ... rather, for 30 days'. 2
Why does the Torah mention these numbers?
Da'as Zekenim: In all, they add to 67 1 , equal to the number of days in a [leap] year when Yisrael must cease Melachah
He counts 29 for "Ad Chodesh." I.e. until then, the merit of Shabbosos and Yamim Tovim will protect you; on day 30, you will die. (He also brings another Perush that I did not understand.