The salt level reported by an SWG is usually just a calibrated measurement of conductivity, not an actual measurement of chloride level (measured as ppm salt) that your test kit measures. The conductivity of your water will vary based on temperature (higher conductivity at higher temperature) and the SWG might not be compensating for that in its display (though usually this problem is seen when the water is too cold and the SWG incorrectly reports a too low salt level). Also, the conductivity will vary based on other ions in the water such as those that come from TA and CYA levels or from sulfates in the water and the SWG may not be adjusting for that if such levels are different from whatever "standard" level that was expected.

Just out of curiosity, what kind of acid do you use -- Muriatic Acid or Sodium Bisulfate? Do you use any sort of non-chlorine shock (potassium monopersulfate)? You could have sulfates in your water that are providing more conductivity but are not measured in the chloride (salt) test kit, but the difference of 1100 ppm seems quite large.

Richard