I took the index with the words, transformed the selection to binary, included 3 zeros, calculated the sha256 digest, took the main part of the hexadecimal to convert it to binary, additional a few zeros to the eight digits of the binary and got 00000010011 which interprets to 19 in https://bookmarkingquest.com/story18761134/bip39-seed-phrase-mnemonics-generator-an-overview