Hmmm... I'm not sure, the test strips for GH show 5 colours (0, 25,75, 150, 300)? Then the KH shows 0, 40,80, 120, 180,300). They show GH as 0 and 25=very soft, 75=soft, 150=hard and 300= very hard. They show the KH as 0,40 =low, 80 =moderate, 120,180=ideal and 300=high. Maybe a different system?