For words that have only three letters, there isn't a 4th letter. For instance with the word “insert”, there aren't any a lot more letters afterwards and so needs to be the word "insert". The word “addict” is while in the BIP39 wordlist however you would have used “addi” for https://bookmarkforce.com/story19119654/new-step-by-step-map-for-ledger-seed-phrase-bip39