For words that have only three letters, there isn't any 4th letter. For instance with the word “insert”, there won't be any extra letters Later on and so need to be the word "include". The word “addict” is within the BIP39 wordlist however , you might have made use of https://worldsocialindex.com/story4063265/helping-the-others-realize-the-advantages-of-bip39-seed-phrase-mnemonics-generator