please someone explain this to me:
[link to www.betemunah.org
On the reverse side of the mezuzah scroll is the Hebrew name of HaShem, Shaddai - שדי. This name is an acronym for:
שׁוֹמֶר דְלָתוֹת יִשְׂרָאֶל
Guardian of the Doors of Israel. Additionally, there are often three words at the bottom of the backside of the scroll: כוזו במוכסז כוזו. These mysterious words, transliterated as: Kozo bemuskaz Kozo. These three words are an altered form of the phrase "HaShem Elokeynu HaShem", which means "G-d, our Lord, G-d". It is actually a form of Gematria (אב׳גד) where each letter is "raised" to the next letter. Thus, an Alef becomes a Bet, and a Bet becomes Gimel, and so on. Here, the letters for HaShem's name yud, hey and vav, hey become caf, vav, zayin, vav (cuzu); and the letters for Elokeynu (alef, lamed, heh, yud, nun, vav) become bet, mem, vav, caf, samach, zayin (bmucsz). Rabbi Moshe Isserlis quotes the Hagahot Maimoni as the source for this custom. It is only a custom and a mezuzah without these words is still valid.