I took the index with the words, converted the variety to binary, additional 3 zeros, calculated the sha256 digest, took the first part of the hexadecimal to convert it to binary, included 3 zeros to your 8 digits on the binary and bought 00000010011 which translates to 19 in decimal. https://nowbookmarks.com/story19504590/the-greatest-guide-to-seed-phrase-bip39