Larry,

I use a FAS-DPD kit (Taylor K-1515A)---using a 25ml sample you will get a resolution on the end point within .2ppm --- That is 2/10ths

The results I posted were a mix of mine and pool store --- Some stores use a colorimeter which yields results to .1 but since I don't trust the stores techniques or calibrations (if they did any) --- you can probably round their numbers off to the nearest whole number.