Testing for chlorine in a FAS-DPD test with a 10 ml sample size makes sense since 0.5 ppm resolution is usually sufficient compared to 0.2 ppm with a 25 ml sample size. Calcium Hardness (CH) is another test where one could use a 10 ml sample size for a 25 ppm resolution. However, for Total Alkalinity (TA), the resolution of 10 ppm with a 25 ml sample size is usually needed. For initial TA adjustments the smaller sample size may be OK, but when making final adjustments the 10 ppm resolution is preferable.