For words that have only three letters, there is absolutely no 4th letter. For instance with the word “include”, there aren't any additional letters Later on and thus needs to be the word "include". The word “addict” is within the BIP39 wordlist however , you might have applied “addi” for https://bouchesocial.com/story20762572/bip39-seed-phrase-mnemonics-generator-an-overview