For words that only have 3 letters, there isn't any 4th letter. For instance with the word “insert”, there won't be any extra letters afterwards and thus must be the word "increase". The word “addict” is from the BIP39 wordlist however, you would've utilised “addi” for “addict”. If you are https://bookmarkhard.com/story19003551/getting-my-bip39-words-to-numbers-to-work