It's common knowledge that the power you can generate at elevation is a lot lower than the power you can generate at sea level, and those of us who ride sometimes at elevation want to be able to calculate how our power at elevation translates into the rest of our power data at sea level. We do this in WKO4 using elevation-corrected power (ecpower), developed by Dr. Andy Coggan to tell us the estimated power output that we would have achieved if we had done the work at sea level. You can also use avg(ecpower) to see the average of this power.
WKO4's elevation correction assumes that mFTP is based on data collected at or near sea level. If most of your training is done at elevation already, using elevation-corrected power (ecpower) will not produce accurate results for you.