For words that have only 3 letters, there is absolutely no 4th letter. One example is with the word “incorporate”, there are no additional letters Later on and so have to be the word "insert". The word “addict” is from the BIP39 wordlist however you might have utilised “addi” for https://bookmarkunit.com/story18672375/how-much-you-need-to-expect-you-ll-pay-for-a-good-valid-bip39-seed-phrase