The RTA-500 is the single supply inverting amplifier module with the gain adjustable by the potentiometer.
Download the RTA-500 datasheet from robothings.pl website.
The RTA-500 single supply application require only the supply voltage and the ADC reference voltage. If the reference voltage is not available the VRef input can be tied to the supply voltage.
The maximum signal values are described in the RTA-500 module datasheet.