This is an adjustable DC-DC regulator with an STN LCD display, which can display the voltage and current at the same time. In this module, it has two buttons to adjust the voltage.
Under the power-off situation, Holding left button and power the supply, when the display begins flashing, release the left button, with a multimeter measuring the output voltage, by press the left and right button, adjust the multimeter measuring voltage near 5V, such as 5.00V, 4.98V or 5.02V is ok too, at this situation, please ignore the displayed on this item. After adjustment, please power off it and then power to it again, then the calibration is completed. Errors can be calibrated in 0.04V, if the error is greater, you can try to calibrate it again.