Need to lower salt level

[Rampo]

Can someone check my math.  If my salt level is reading 2500 ppm but should be 1750 ppm how much water should I replace in a 210 gal spa?  (I made a dumb mistake and added too much salt during initial startup).  To correct the high salt level, this is how I calculated that 90 gallons should be replaced with fresh water:  2500 current ppm /1750 desired ppm =1.43 then  subtract 1 and multiply 0.43 X 210 = 90.3 Gal.  Seems to me that's like a lot of water to be drained.  If I  do the same calculation, but plug in the upper salt limit of 2200 ppm, then it comes out to about 30 gallons to be replaced.  Maybe I'll start by draining 60 gallons and take a measurement at that point before draining any additional?