Certification EPNL is corrected to a standard sea level airfield, ISA+10, 70%RH and nil wind. The certification test measurements are corrected for the calculated heights etc. for the differences to the test day.
The take off measuring station is a fixed distance from the start of ground roll, so height can vary a lot depending on conditions.
For the approach condition the thrust must be set at what the manufacturers have calculated for those standard day conditions at MLW and nil wind with a flyover height of 394 ft.