Saartje's Bootees Straps?

So I know how to cast on using the long tail method but I’m not quite sure I understand row 25 of the Saartjes Bootees pattern. It says to “co 10 using the long tail cast on and second strand of CC as the thumb strand, cut second strand leaving 8” tail" but I don’t understand what to do and the pictures aren’t helping me much. Can anyone explain to me how this works?

Use another strand of yarn for the thumb yarn and CO. Or you could forget the other yarn end and use a cable cast on instead.

Someone else also had problems with that row, so I made a video. Hope this helps.

Fantastic! Thanks so much, I’m gonna try right now.