The EMX / EMX2 current display can be calibrated by adjusting the value in parameter 13. If the EMX is reading high, reduce the value in parameter 13. If the EMX is reading low, increase the value in parameter 13.
To calculate the new value for parameter 13, measure the actual current Ia, and divide this into the displayed current Id. Then multiply this by the old value in parameter 13. The result is the new value to store in 13.

Worth noting that the displayed amps is the average amps accross the 3 phases.

Therefore when 'calibrating' the starter my advice would be that you need to measure current in all 3 phases, add together and divide by three to get the average and prior to performing calculations suggested by Marke.

What may not be so apparent is that this process reduces the tolerance/error in the current sensing circuits thereby fine tuning all current based protection functions. Quite often the display will read high, which means the starter thinks more current is passing than actual. This can result in unecessary overcurrent trip. The calibration process can eliminate those also.

Same process applies to the EMX, IMS2 & EMX3 products albeit that a different parameter (not parameter 13) is used.

With legacy product such as the EMS & IMS it may be necessary to adjust the motor FLC stetting to compensate for any CT or current sensing circuit error.