For words that only have three letters, there is no 4th letter. For instance with the word “include”, there isn't any much more letters afterwards and thus needs to be the word "insert". The word “addict” is within the BIP39 wordlist but you would have applied “addi” for “addict”. Ways https://bookmarknap.com/story9032133/how-much-you-need-to-expect-you-ll-pay-for-a-good-valid-bip39-seed-phrase