According to the manual this board has 2 analog inputs with attenuation and amplification option.
Page 10 in the manual gives a guidance how to amplify a voltage lower than 5 V.
But why if you want to monitor a voltage of 30V, how do you make the attenuation, the analog input must not extent 5V.
The K8055 input resistance is 100kΩ, so all you have to do to accommodate higher input ranges is place an appropriately sized resistor in series with the input.
To measure a 30V level you would need to use a 500kΩ resistor. However as this is not a commonly available standard resistor, and the K8055 input resistance is not that precise, use a 1MΩ potentiometer.
It would be best to use a 10-turn pot, and use it to closely calibrate the voltage drop.
Also, keep in mind that the resolution (0.02V¹) of the K8055 will be multiplied (degraded) by a factor of 6 relative to the original input level. So the minimum change in the 30V input that can be observed will be 0.12V.
¹ - This is theoretical resolution of the 8-bit ADC used in the K8055, in practice it will be less precise (a higher value)
Thank you for your answer and the very fine explanation.