For words that only have 3 letters, there's no 4th letter. For instance with the word “insert”, there are no a lot more letters Later on and so should be the word "insert". The word “addict” is within the BIP39 wordlist however , you would have utilized “addi” for “addict”. https://reallivesocial.com/story4355085/new-step-by-step-map-for-ledger-seed-phrase-bip39