The slider represents the input analog sensor that reads the psi. So to the left means a low pressure and to the right means there is a high pressure reading.
The LEDs represent the relays. Violet for the valve, Orange for the compressor, cyan for the concentrators.
The programs starts the concentrators, compressors and the valves when the reading is below 40 psi and stops at 85 psi. So 40 and 85 are trigger points.
The added complexity is that when it starts there is a delay for the valve for 15 seconds.
And in turn when it has to stop there is a delay of 30 seconds before valve is switched off.