Detection limit for Wal-Mart kit CH test??

[waterbear]

250 ppm CH is fine. Why add more?

[Henrys514]

I'm not sure I trust my test...I tested again yesterday and I got 300ppm this time, and that's after 2+ inches of rain. I didn't add anything yet. I'm going to take the water into the pool store today because I need to get the CYA tested and I'm out of reagent. I'll see what their numbers say, then test my water myself, then I'll post both results, and we can see where we are at.