For words that only have 3 letters, there isn't a 4th letter. By way of example with the word “increase”, there isn't any extra letters afterwards and so has to be the word "include". The word “addict” is in the BIP39 wordlist however , you would have employed “addi” for https://socialbuzzmaster.com/story4391928/the-fact-about-valid-bip39-seed-phrase-that-no-one-is-suggesting