Thanks Mark. My overall tank volume including sump is around 450 liter which is probably around 118 gallon.
I agree and not aiming to have a straight line. But rather, notice that my dosing is way out of the recommended range. I am using the calculator which you shared but just couldn't seem to get the reading to correlate to the actual value. The most concerning part is the speed of KH drop which again, seem to be abnormal.
Tried to stop dosing for a day follow by only dosing KH at small value but it doesn't seem to gradually increase which is what I am hoping. I am taking the assumption that with minimum coral, assuming the tank will only consume less than 0.5dKH per day, if my dose is aim at 1dKH as per the calculator, i should see a gradual increase day by day and eventually, fine tube the dose to stabilize it. However, not able to achieve any logical approach to tackle this abnormally.