mathematics where 200/80=5?
Imma try and puzzle it out. We can estimate that there were 83561 emails sent in the campaign. We can verify this approximation because the percent opened mostly matches (212877/83561 = 254.75%).
So, if everyone opens a certain number of them, that number is a part of the stated percent. If for example there were only 100000 emails sent and you opened 100, there are 1000 100s in 100000 so therefore you opened 10 percent. Now, if you only opened up 5 emails... well I can't figure out just five, so we'll pretend they opened up five, so that's 10 percent five times over again and you get 250%, yeah?