For words that have only three letters, there is not any 4th letter. Such as with the word “include”, there are no extra letters Later on and therefore need to be the word "include". The word “addict” is in the BIP39 wordlist however, you would've employed “addi” for “addict”. You https://bookmarkbirth.com/story18912131/a-secret-weapon-for-bip39-words-to-numbers