Unity Ads revenue is generated from the time an Ad/video is started. Once started, 'impressions' start to generate. Please note: Impressions are counted each time a video is started. Only every 23rd Ad request is recorded due to sampling. If you have only a handful of Ad requests per day, only every 13th of them is added to the statistics page.
Typically it takes around 5000 impressions or more to determine the quality of the users you are sending. You will be getting revenue based on the quality of your user impressions.
Unity Ads generates revenue through generating views and traffic from your game, and you get paid based on that. There is no "one unified way" of pre-calculating the revenue generated to you, as we run different types of campaigns (with different billing points, for example completed views, clicks or installs). Our system always selects the best (in terms of money) possible campaigns for your users.