The i5-3210M can support DDR3-1600 by default, and according to what you posted you're running at DDR3-1600 (798*2 = 1600 appx).
Again, I wouldn't mix DDR3-1600 & DDR3-1333 so if the deal is good then get (8GB) 2x4GB DDR3-1333. The difference is negligible.