For words that have only 3 letters, there isn't any 4th letter. Such as with the word “incorporate”, there are no more letters Later on and thus needs to be the word "include". The word “addict” is during the BIP39 wordlist however you might have employed “addi” for “addict”. A https://bookmarkindexing.com/story18726942/getting-my-bip39-words-to-numbers-to-work