For words that only have 3 letters, there isn't any 4th letter. As an example with the word “include”, there are no far more letters Later on and therefore must be the word "increase". The word “addict” is from the BIP39 wordlist but you might have utilised “addi” for “addict”. https://bookmarkinglive.com/story19844894/helping-the-others-realize-the-advantages-of-bip39-seed-phrase-mnemonics-generator