For words that only have 3 letters, there is absolutely no 4th letter. One example is with the word “insert”, there isn't any additional letters Later on and therefore needs to be the word "insert". The word “addict” is during the BIP39 wordlist but you would have utilized “addi” for https://1001bookmarks.com/story19482525/5-simple-techniques-for-bip39-word-list-pdf