Hayward Omnilogic with T940 salt cell and Taylor K-1766

The displayed value for Instant and/or Average Salt shown on the Omnilogic Chlorinator Diagnostics screen is always about 400 ppm high when compared to the Taylor K-1766 drop test.

Does the Omnilogic actually display a TDS value and not a true NaCl salt value?
Also, for salt readings:
Is the Taylor K-1766 accuracy +/- 200 ppm?
Is the Omnilogic accuracy +/- 400 ppm?

Any help appreciated.