For words that have only 3 letters, there isn't a 4th letter. For example with the word “increase”, there aren't any far more letters Later on and thus need to be the word "insert". The word “addict” is during the BIP39 wordlist however you would have utilised “addi” for “addict”. https://seobookmarkpro.com/story18970494/the-ultimate-guide-to-bip39-seed-phrase-mnemonics-generator