For words that have only 3 letters, there is not any 4th letter. One example is with the word “include”, there aren't any more letters Later on and so have to be the word "add". The word “addict” is from the BIP39 wordlist but you might have made use of https://social-lyft.com/story8647347/how-much-you-need-to-expect-you-ll-pay-for-a-good-bip39-seed-phrase-mnemonics-generator