Air Conditioning System Repair. Performed service diagnostic. Diagnostic found that the system was performing poorly. Sub cooling was very low, and the temperature split from return to supply was 8-10 degrees. Design sub cooling was checked through the service application on the thermostat control and the system determined a designed sub cooling of 18 degrees. Two pounds of R-410A was added to bring the sub cooling up to 18 degrees. Temperature split had improved to 14-15 degrees before I left. Return temperature was 70 degrees, supply temp was 55 degrees and outside air was 97 degrees. I asked the customer to monitor that system and let us know if it continues to have cooling issues. System was running at the time of departure