For words that only have three letters, there is absolutely no 4th letter. By way of example with the word “incorporate”, there are no extra letters afterwards and so must be the word "insert". The word “addict” is inside the BIP39 wordlist however , you might have utilized “addi” for https://bookmarktiger.com/story18792378/a-secret-weapon-for-bip39-words-to-numbers