For words that only have 3 letters, there's no 4th letter. For instance with the word “increase”, there aren't any more letters Later on and thus need to be the word "add". The word “addict” is from the BIP39 wordlist however you might have utilized “addi” for “addict”. BIP39 and https://wisesocialsmedia.com/story4257543/invalid-bip39-phrase-things-to-know-before-you-buy