what do you want to know about it...certainly its covered in the POH.
the different abbreviations are for different phases of flight...and will produce the MAX epr for temp and phase of flight
takeoff, climb, cruise, go around.
enter the data (temp) and the phase of flight and you get the EPR.
.does it automatically move the epr bug? or do you have to set that after reading the output.
if you are flying the plane and don't know how to get the EPR, you can look it up in the tables in the book...the gadget takes less time than pulling out the book.