For words that only have 3 letters, there is no 4th letter. By way of example with the word “increase”, there isn't any much more letters Later on and so should be the word "include". The word “addict” is within the BIP39 wordlist however you might have utilised “addi” for https://adsbookmark.com/story19189539/considerations-to-know-about-bip39-word-list-pdf