I am kind of new to this pool stuff...and still waiting for my test kit....?????

In the meantime

My chlorine has been in good ranges not too high, not too low
My CYA is a little low (about 27 or 28) i heard it dissolves slowly in the sand filter so dont jump and add more for afew days....yes
My PH has been rising and is now a little over 8...maybe 8.2
Hardness is around 230
My alkalinity seems to be in the range of 100

Am i correct to add some acid? 17500 gallons...what is a good dose to begin correction?