I've decided to not worry about the yardage on the mystery yarn at least until I finish with the sampler shawl. I did have to buy another skein of yarn for that shawl. It arrived this past week. I reluctantly balled it up and started the endless edging.
Here it is so far. I haven't been working on it as much as I did when I was doing the main section. The border gets boring after a while. Each repeat is only 12 rows and between 7 and 14 stitches wide. It's easy to memorize and easy to do. In the photo above, I've complete 27 out of 140+ repeats. Below is a close-up of the border.
I can't wait until this project is done. Not because it has taken a long time, but because I want to do so many other shawls out of that book. I'm holding myself back from casting on for another one before this one is finished.