How does Akanoo calculate the additional revenue?

Every visitor is assigned to either a test group or a control group. Members of the control group do not get incentivised.Based on the revenue and impressions of each group, the additional revenue is then calculated as follows:

Additional Revenue = Revenue Test Group - ((Impressions Test Group / Impressions Control Group) * Revenue Control Group)

Which data are tracked by Akanoo?

Are there legal requirements to use Akanoo?