For words that only have three letters, there is not any 4th letter. By way of example with the word “include”, there won't be any far more letters afterwards and so should be the word "add". The word “addict” is while in the BIP39 wordlist however you would have applied https://bookmarkcork.com/story19498506/new-step-by-step-map-for-ledger-seed-phrase-bip39