My Apex salinity reading has drifted over the past few months, not far, but enough to give it a quick calibration. My Hanna gives a solid 35ppm. I'm sure I've previously done a manual calibration where I've just left the probe in the sump and run the calibration - granted, I've not done one in maybe 18 months. But now it seems the manual calibration steps want the 53,000 µS/cm solution. Is there a way to still do this? I just want to tell my probe the salinity level is at 35ppm!