Calcium deposits?

[halefmly]

I just went to the Pool $tore for a replacement bag for my Pentair Pool cleaner, and decided to get a water test. Since the post above, I have kept my Alkalinity down between 80 and 90 for the past two months. (quite a feat with the highly Alkaline water supply in North Texas). Well, the Pool $tore said that I needed to get my Alk up to 100 to prevent "etching the plaster."

Is this real? Should I worry about it? What is the worst thing etched plaster can do?

The Pool $tore numbers are:

FC: 9.4
CC 0.6
TC 10
pH 7.1
Alk 88
TDS 4700
Cya 80
Temp 74
Salt 4000

My numbers with the PS234s:
FC: 11
CC 0
TC 11
pH 7.6
Alk 80
Cal 500
Cya 60
Temp 65
Salt 3600
Do you have any wisdom to share on the Alkalinity and on the variance in the numbers?