What was your pH before CO2? The purpose of the chart is to determine your target pH based on your KH. Adjusting your KH won't help because pH is directly tied to KH (ideally) and you'll come out with the same CO2 levels after you do the math. In other words, adding CO2 at 4bubbles/sec with a KH of 3 should give you roughly the same concentration of CO2 with a KH of 6. The problem with using the chart is that in some situations, the pH is thrown off by other things. A good check to see if your setup follows the KH/pH/CO2 equation is to measure pH and KH after the tank is idle for 24hours without co2. Apply the values to the table and you should see 2-3ppm CO2. If not, then you'll have to adjust the table accordingly. Assuming a KH of 3-6deg, a 1pH drop from CO2 injection equates to safe levels of CO2. A drop checker is probably the easiest and most reliable way of monitoring CO2.