Used formula to calculate power consumption

Hello,

I have a question, as far as I know the current clamps used with the flukso measure current and have no clue of voltage, so to calculate the power consumption I assume they use a fixed voltage setting?

To which amount is this set and where is this configured ?
e.g. depending on the moment of the day the voltage in my home is somewhere between 231 and 237 volt.

I have a separate volt meter I could read out from the flukso to always use the current voltage to calculate the real power consumption, ...