Bip39 entropy to mnemonic https://www.gamespot.com/profile/pothirpeib/ Checksum creation: A checksum is produced from this entropy using SHA-256 hashing, which will help confirm the mnemonic's integrity afterwards. For words that only have three letters, there isn't any 4th letter. One example is Using the word “include”, there aren't any far more letters https://telegra.ph/Producing-Custom-Bitcoin-Addresses-A-Take-A-Look-At-BIP39-Strategies-06-28