For words that have only three letters, there's no 4th letter. By way of example with the word “incorporate”, there are no additional letters Later on and thus have to be the word "include". The word “addict” is from the BIP39 wordlist however you would've utilized “addi” for “addict”. This https://socials360.com/story9295713/invalid-bip39-phrase-things-to-know-before-you-buy