For words that only have three letters, there's no 4th letter. One example is with the word “insert”, there won't be any far more letters Later on and so have to be the word "incorporate". The word “addict” is inside the BIP39 wordlist however, you might have used “addi” for https://digibookmarks.com/story18821815/ledger-seed-phrase-bip39-no-further-a-mystery