VC,
My pool was built about the same time and my IC40 was never close to the actual salt readings. This year it seemed to be even worse, always way low. I called my pool builder, he sent out a warranty repair tech who replaced the flow switch assembly, which also has a temperature sensor for the SWG itself. Now the SWG reads pretty close to the actual salt readings.
Since your system is so new, I suggest you call your PB first. Worse case you can buy a new flow switch for about $100.
Jim R.