For words that have only 3 letters, there is not any 4th letter. One example is with the word “incorporate”, there are no extra letters afterwards and so should be the word "increase". The word “addict” is while in the BIP39 wordlist but you would have applied “addi” for “addict”. https://getsocialpr.com/story20023036/helping-the-others-realize-the-advantages-of-bip39-seed-phrase-mnemonics-generator