Mineral Solutions DMSO is exactly what it says on the label - 99.8% DMSO and 0.2% pure water. It is unclear why pharmaceutical grade is lower than industrial grade (often claimed as 99.9%) but it is pharmaceutical grade. Once opened it will start to accumulate water, as you will see if you put it in a refrigerator and not that not all of it solidifies at that temperature.
If you wan to dilute with water then you can, but it isn't pre-diluted. Most people can use it as is, but if you have sensitive skin, then due to it's attracting properties it can pull water out of the skin and cause a little drying, in which case you might want to dilute with water or Aloe Vera or similar.