For words that have only 3 letters, there's no 4th letter. As an example with the word “increase”, there isn't any more letters Later on and so needs to be the word "add". The word “addict” is inside the BIP39 wordlist but you would have utilized “addi” for “addict”. gravity https://yesbookmarks.com/story19703171/a-secret-weapon-for-bip39-words-to-numbers