test kit by Aquariumpharm( www.aquariumpharm.com
As indicate in the test kit that
" The Carbonate Hardness value is determinedby the number of drops of the reagent that must be added to turn the water in the test tube bright yellow. Each drop is equal to 1* dkh
or 17.9ppm KH
So when i tested the water, by the 3-4th drop the water turn from blue to yellow. So i assume to be 3-4dKH.