For words that have only three letters, there isn't a 4th letter. One example is with the word “insert”, there are no a lot more letters Later on and so need to be the word "incorporate". The word “addict” is during the BIP39 wordlist however you would have utilised “addi” https://ilovebookmarking.com/story19025505/the-greatest-guide-to-seed-phrase-bip39