For words that only have three letters, there's no 4th letter. By way of example with the word “insert”, there won't be any extra letters Later on and therefore need to be the word "add". The word “addict” is from the BIP39 wordlist however you would have utilized “addi” for https://thegreatbookmark.com/story18873238/bip39-phrase-generator-can-be-fun-for-anyone