For words that have only 3 letters, there isn't a 4th letter. One example is with the word “add”, there isn't any additional letters Later on and thus has to be the word "insert". The word “addict” is during the BIP39 wordlist but you would've made use of “addi” for https://socialskates.com/story20906575/little-known-facts-about-bip39-seed-phrase-list