That looks like good stuff and almost half the price of the Motorcraft!I would say about 1 large bottle of the Pentosin Dot (4LV) fluid, to be good enough and the service manuals do not give this information either, you want to leave room for the bleed.
In my search I saw the 3rd gen non-US ranger took 1.25L.Most vehicles will take 1 quart of brake fluid. It's when you get to the heavy duty trucks and stuff that the capacity is a bit more.