Bip39 Checksum. Since the 24th can be a checksum word, a list of eight legitimate candidate words are calculated using the Python script 24thword.py. For words that have only three letters, there is no 4th letter. One example is Along with the word “increase”, there isn't any additional letters afterwards https://directory-nation.com/listings13193407/bip39-mnemonic-code-converter-tool-https-linktr-ee-bip39-facts-about-bip39-checksum-revealed