For words that only have three letters, there is not any 4th letter. One example is with the word “incorporate”, there isn't any extra letters Later on and so need to be the word "insert". The word “addict” is inside the BIP39 wordlist but you might have used “addi” for https://bookmarkleader.com/story18846040/an-unbiased-view-of-bip39-seed-phrase-github