For words that only have three letters, there isn't a 4th letter. For example with the word “insert”, there aren't any more letters Later on and therefore should be the word "include". The word “addict” is while in the BIP39 wordlist however you might have utilized “addi” for “addict”. Finding https://naturalbookmarks.com/story18978533/a-secret-weapon-for-bip39-words-to-numbers