Now calibrate the controller - this is done in varying ways as follows depending on the controller:-
a) use the up and down arrow keys to change the display until it reads the correct EC value or as close to this as possible then SAVE this calibration
b) type in the correct value and save this
c) press SAVE to automatically calibrate at EC 2.76mS/cm
d) use a screwdriver to carefully turn the CAL screw (Autogrow does not use this method but some older equipment may still use this)