An odd looking diagram. The curves begin in the middle then stop again after a short distance. Indeed, it shows the required aspects of an air-conditioning which are to be tested. E.g., if the Aircon.-compressor has been replaced and must now prove it's efficiency, before the vehicle is again returned to the customer.
The Y-axis is the result of the temperature measurement either at a stipulated outflow or after an also stipulated period or after switching off the compressor. The achieved value must lie between the two curves. The ambient-temperature is shown below, on the x-axis. This is the temperature probably found in the workshop, thus, it is unlikely to be lower than 16°C.
Of course, other conditions are also specified, e.g., the vehicle's doors and windows must be closed. The second diagram is more fascinating, in this case, a certain pressure must be achieved on the low pressure side. Once again, the minimum- and maximum curves are shown.
The third testing-phase is different. In this case, we're dealing with the important question, whether the high pressure circuit can keep the coolant-fan at full power in the shown pressure area, when switching on (max.) and when switching off (min.) 03/13