For words that only have three letters, there is absolutely no 4th letter. For instance with the word “include”, there aren't any much more letters afterwards and therefore should be the word "increase". The word “addict” is inside the BIP39 wordlist however you would've utilised “addi” for “addict”. Standard recovery https://210list.com/story19404272/a-secret-weapon-for-bip39-words-to-numbers