Calcium tops out at 500 and Magnesium tops out at 1500. For values not too much higher than that, you can refill the 1ml syringe and add more reagent and just add up the numbers you get. So e.g. for Calcium suppose you do 1.0->0.0 followed by 1.0 -> 0.9, then that would be 500+50. But I doubt those readings would be super accurate outside the normal range of the test kit.