In this case, "it" is the spinning - with the first bobbin all done and completely filled:
The second bobbin is not full yet, but as soon as it is, I will wind skeins from both of them, measure the amount done, weigh them, and set the twist. And then the rest will be spun.
I'm starting with the weft in this case, and I'm trying to make it a little bit thicker than in the test run; same will happen with the warp. The weft in the originals is rather unevenly thick and thin, so I'm sort of trying to not pay too much attention to thickness while staying in the appropriate range.
It's funny how trying to match a non-perfect original thread is about as hard (though maybe in a different way) than trying to match a really well-done, almost perfect original thread!