For words that have only three letters, there's no 4th letter. Such as with the word “increase”, there aren't any much more letters Later on and therefore needs to be the word "increase". The word “addict” is from the BIP39 wordlist however you would have utilised “addi” for “addict”. Protection: https://bookmarklinking.com/story5381616/the-definitive-guide-to-bip39-seed-phrase