For words that only have three letters, there's no 4th letter. For instance with the word “insert”, there isn't any a lot more letters afterwards and so has to be the word "include". The word “addict” is while in the BIP39 wordlist however, you would've made use of “addi” for https://digibookmarks.com/story19567305/the-basic-principles-of-bip39-passphrase-generator