Yes, add more. It's not too late. As far as dumping the previous 1/4" left over, that's probably a Trapper question, but offhand I don't think I would have dumped it. Just add more water and continue. It's probably preferable to start each batch fresh, but in an accident, I'd use the liquid I could and then add water and shake/stir till just a bit was left in the bottom of the container to indicate continued saturation.