For words that only have 3 letters, there's no 4th letter. Such as with the word “insert”, there are no far more letters Later on and thus must be the word "add". The word “addict” is during the BIP39 wordlist however , you would've utilised “addi” for “addict”. A number http://hectorswwo172.bearsfanteamshop.com/understanding-your-copyright-security-the-crucial-guide-to-bip39-passphrases-and-mnemonics