For words that have only three letters, there isn't a 4th letter. One example is with the word “add”, there isn't any a lot more letters afterwards and so has to be the word "increase". The word “addict” is while in the BIP39 wordlist however , you might have employed https://livebookmarking.com/story19004347/new-step-by-step-map-for-ledger-seed-phrase-bip39