Happy New Year!! Thanks to this board I've got a good understanding of the chemistry now, but the CSI thing on the calculator has me confused. It seems most recommendations for CH are 250-350, my 2 mo old plaster is at 280. When I plug my readings in, it says I need to raise my CH to 450 to get the rec. CSI of -0.6......that seems to be high from I've read, what do you think?