Cheth = 8, ordinal 8, reduced 8, no final form. Spelled in full, חית = 8+10+400 = 418.
Meaning
Cheth is 'fence' or 'enclosure', one of the twelve simples, and the letter that opens חכמה, חיים and חסד — wisdom, life and mercy — which is why the Kabbalists treat it as the letter of the enclosed and the protected. Its 8 is the number of circumcision, performed on the eighth day, so the letter sits at the boundary between the week and what exceeds it.