For words that only have three letters, there is no 4th letter. For example with the word “incorporate”, there aren't any far more letters afterwards and so needs to be the word "include". The word “addict” is in the BIP39 wordlist but you would've used “addi” for “addict”. Locating a https://maximusbookmarks.com/story19049897/a-secret-weapon-for-bip39-words-to-numbers