Why is there a difference between clicks in "Overview" campaign report page and clicks in the "Clicks" report page?

Metrics in the Overview report page refer to contacts. Metrics in the Clicks report page refer to the clicks themselves.

Example:

1. You send a campaign.

2. The campaign message has two links in it.

3. The campaign is sent to three contacts: Jane, Kate, and Shirley.

4. Jane doesn't click any link.

5. Kate clicks both links, but just once each.

6. Shirley clicks only one of the links but clicks it twice

7. This will be represented in the report as:

   • "2 out of 3 contacts" in the Overview report page, because Jane didn't click any link at all.

   • "4 total clicks" in the Clicks report page, because Kate clicked two links, once each (1+1=2) and Shirley clicked the same link twice (1+1=2), that totals to 4 clicks

   • "3 unique clicks" in the Clicks report page, because Kate clicked two links, once each (1+1=2), and Shirley clicked the same link twice. For unique clicks, only the first time the link is clicked is counted.