Can anyone explain why the Red Sea Refractometer PPT scale mark at 0 does not line up with the SG scale at 1.000. The PPT scale is clearly off set a bit with respect to the SG scale. Shouldn't 0 PPT equal 1.000 SG. I found two conversion calculators online that that convert 0 PPT to 1.000 SG at 25 deg C. Why would Rea Sea offset these scales. I am new to reefing and I have not been able find any info to explain this.
