For words that have only 3 letters, there's no 4th letter. As an example with the word “increase”, there won't be any extra letters afterwards and thus has to be the word "increase". The word “addict” is while in the BIP39 wordlist however , you would have utilised “addi” for https://loanbookmark.com/story18878014/not-known-factual-statements-about-bip39-explained