For words that have only three letters, there isn't a 4th letter. As an example with the word “include”, there are no far more letters afterwards and thus should be the word "insert". The word “addict” is while in the BIP39 wordlist however you would have used “addi” for “addict”. https://toplistar.com/story21461125/5-simple-techniques-for-bip39-seed-phrase