Just at first glance I would say it's higher a gigantic sett, or the white line in the middle is being used to mirror the sett. The thick dark blue/black stripes are on opposite sides of their respective light blue stripes.

The answer to that riddle is probably the same for why there's only one thick dark stripe near the end of the piece horizontally. The thin stripes repeat like a sett, but the thick striped seems to once again be forming a border of sorts.

Finally, I dont know if it's just my eyes, the shading difference or what, but several of the thin blue stripes to the right of center seem to smaller thread count than their partners to the left.