For words that have only three letters, there is no 4th letter. For example with the word “add”, there isn't any additional letters afterwards and so has to be the word "add". The word “addict” is from the BIP39 wordlist but you might have used “addi” for “addict”. Safety: Any https://ok-social.com/story4269121/the-fact-about-valid-bip39-seed-phrase-that-no-one-is-suggesting