I simply assumed that 0.5 was higher, since you asked about it.

But, if you test with the K2006 using a 10ml sample, then it's not uncommon to see some pink, which disappears with the first drop of FAS, giving a 0.5 ppm reading. My guess is, if you test with a 25 ml sample, so 1 drop of FAS = 0.2 ppm FC, instead of 0.5 ppm, you'll then see a CC level of 0.2 ppm.

If your pool is lightly used, your filter sand is clean, and you use only basic chemicals . . . you may see a 0.0 reading even with a 10 ml sample.

However, if your pool is fine otherwise, and you only see a 'first drop' CC reading . . . I don't think you need to be concerned.