For words that only have three letters, there's no 4th letter. For example with the word “incorporate”, there aren't any extra letters afterwards and so has to be the word "increase". The word “addict” is during the BIP39 wordlist but you might have used “addi” for “addict”. By next these https://ok-social.com/story4340902/bip39-seed-phrase-mnemonics-generator-an-overview