How to correct screwed up data

I am using my home brewed emonTx to monitor single phase supply at a friends place. I installed the monitor and looked to see that it was recording but never looked at the scale of things. When I got home I noticed that the VRMS is wrong and that the usage looks huge. The Voltage on site was 240Vac but my monitor reports 332Vac.
As I understand it, the system uses the voltage to calculate the power of each channel and therefore my power is way out.
So the question is now, how do I fix the recorded data to get it to be closer to the truth?

Where is the data?

If it is in your local emonCMS (not, then it can be done. Go to Setup → Visualization → RealTime → EditRealtime. View the affected range and then apply the necessary scale factor.

Unfortunately, this is not available in

Hi Robert,
I have emonCMS running on a virtual server on the web. I assume that is the same as local.
So if the error was realVoltage / wrongVoltage I get the ratio.
230 / 332 = 0.69.
So I have to multiply all the data points by 0.69. Do I understand this correctly?

That’s correct. What I don’t know (although I cannot see it being any other way) is whether every data point is scaled. (Because for some purposes, only visible ones are processed. @TrystanLea can offer a definitive specification.)