For words that have only three letters, there's no 4th letter. One example is with the word “insert”, there won't be any far more letters Later on and thus needs to be the word "include". The word “addict” is in the BIP39 wordlist however, you would have used “addi” for https://socialstrategie.com/story4538130/a-secret-weapon-for-bip39-words-to-numbers