For words that have only 3 letters, there's no 4th letter. As an example with the word “add”, there aren't any much more letters afterwards and therefore needs to be the word "insert". The word “addict” is while in the BIP39 wordlist but you would've utilized “addi” for “addict”. Discovering https://webcastlist.com/story19964733/helping-the-others-realize-the-advantages-of-bip39-seed-phrase-mnemonics-generator