Bip39 date https://www.spreaker.com/podcast/palerioiwk--6670096 Checksum generation: A checksum is generated from this entropy employing SHA-256 hashing, which helps validate the mnemonic's integrity later on. For words that only have 3 letters, there is absolutely no 4th letter. One example is with the word “add”, there aren't any a lot more letters https://bookmarklogin.com/story20188028/bip39-format-5-simple-statements-about-bip39-converter-explained-https-www-youtube-com-channel-ucupxfytj0fb78sq55hu6ocw