Your email campaign engagement rates are calculated wrongly.

E.g. if I send to 1000 people, 900 was delivered successfully, 200 opened, 20 clicked, 5 unsubscribed

Current calculation method returns:

90% delivery rate (900/1000 - total received/total sent)
22.2% open rate (200/900 - total opened/total received)
10% clicked rate (20/200 - total clicked/total opened)
0.56% unsubscribed (5/900 - total unsubscribed/total received)

All numbers should be divided by [number of people SENT] instead. The example above should return:

90% delivery rate (900/1000 - correct)
20% open rate (200/1000 - total opened/total sent)
2% clicked rate (20/1000 - total clicked/total sent)
0.50% unsubscribed (5/1000 - total unsubscribed/total sent)