For words that have only three letters, there's no 4th letter. One example is with the word “include”, there won't be any additional letters Later on and therefore need to be the word "include". The word “addict” is from the BIP39 wordlist however, you would have made use of “addi” https://bookmarkwuzz.com/story18821398/the-5-second-trick-for-ledger-seed-phrase-bip39