For words that only have 3 letters, there is no 4th letter. For instance with the word “add”, there are no much more letters Later on and therefore has to be the word "include". The word “addict” is from the BIP39 wordlist however , you might have used “addi” for https://bookmarkstumble.com/story20460232/the-fact-about-valid-bip39-seed-phrase-that-no-one-is-suggesting