For words that only have 3 letters, there isn't any 4th letter. For example with the word “insert”, there aren't any extra letters afterwards and thus have to be the word "add". The word “addict” is in the BIP39 wordlist but you would've utilized “addi” for “addict”. You signed in https://livebookmarking.com/story18828325/detailed-notes-on-copyright-wallet-seed-phrase-out-of-bip39