Pressure altitude calculations
Calculate PA for an airfield at sea level and altimeter setting of 29.32 or QNH 993mb
Taking the above calculation into account the aircraft at the airfield at sea level would in fact perform as if it were already at 600ft above sea level. Therefore a longer take off run would be expected before actually getting airborne or your multirotor propellers would need to spin at a higher RPM before the RPA would lift off.
How does PA affect RPAS operations? If your area of operation is currently under a high pressure then you could expect better performance and longer battery run times. The opposite would be true for low pressure conditions.