Bip39 Checksum. If you would like to refresh your memory about the basics of how copyright wallet seed phrases and passphrases get the job done, think about reviewing the Vault12 report in regards to the BIP39 standard. For words that have only 3 letters, there is absolutely no 4th letter. https://real-directory.com/listings13148212/bip39-seed-generator-https-linktr-ee-bip39-bip39-list-options