For words that only have 3 letters, there isn't any 4th letter. By way of example with the word “add”, there isn't any a lot more letters afterwards and so need to be the word "insert". The word “addict” is while in the BIP39 wordlist however you might have made https://www.symbaloo.com/embed/shared/AAAACHlsY-AAA42AhQqHKA==