For words that have only three letters, there isn't any 4th letter. By way of example with the word “insert”, there aren't any much more letters afterwards and therefore must be the word "add". The word “addict” is while in the BIP39 wordlist however , you would have utilised “addi” https://bookmarkproduct.com/story19702362/considerations-to-know-about-bip39-seed-phrase-generator