As stated above, ditch the strips and get a drop kit. Taylor's can be ordered online, as well as Ben's.

Once you can verify the salt level, go to www.autopilot.com and download the manual for your unit. That will tell you how to calibrate.

I've got a DIG-220, and I recalibrated it after installation. I figure it it's +/- 100 ppm vs. the drop test, it's good to go.