For words that only have three letters, there's no 4th letter. Such as with the word “include”, there won't be any additional letters afterwards and therefore needs to be the word "include". The word “addict” is from the BIP39 wordlist however you would've utilized “addi” for “addict”. This information clarifies https://bookmarkstown.com/story19036942/helping-the-others-realize-the-advantages-of-bip39-mnemonic-phrase-tool