For words that only have 3 letters, there is not any 4th letter. For instance with the word “incorporate”, there aren't any much more letters Later on and thus need to be the word "include". The word “addict” is inside the BIP39 wordlist but you might have used “addi” for https://bookmarkswing.com/story20265923/getting-my-bip39-words-to-numbers-to-work