[DarkCobra]

Any drop checker is likely to give wildly false readings if you fill the bulb with aquarium water. And I believe that's what the ANS instructions tell you to use.

For accurate readings, you must use a solution of exactly 4 degrees carbonate hardness, commonly known as a 4DKH solution. I've seen them for sale on the Swap 'n Shop here, Ebay, various other places. Then add 2-3 drops from a standard pH test kit. Do NOT use the indicator included with the drop checker. In my experience, if it tells you to use tank water, the included indicator is usually faulty too.

 

[DarkCobra]

Probably. The pH/KH method of CO2 measurement is highly dependent on both accurate measurements, and carbonates being the only significant alkaline buffer. But at 8ppm, even if it's reading half the true CO2 amount (16ppm), you can still double the amount of CO2. Just keep an eye on the fish, they'll tell you if something is wrong.