I took the index of the words, transformed the selection to binary, extra a few zeros, calculated the sha256 digest, took the very first Element of the hexadecimal to transform it to binary, extra 3 zeros to your eight digits on the binary and obtained 00000010011 which interprets to 19 https://wisesocialsmedia.com/story4272881/bip39-seed-phrase-mnemonics-generator-an-overview