Sorry for the delayed response! It displays overall clicks. The way I determine unique clicks is through the Email Link Performance report. You'll see a Clicks and a Leads column. My Clicks column is usually higher than Leads so some leads have clicked on the link more than once.
The following may clarify things:
- In the Email Link Performance Report, "Clicks" counts the number of times that link was clicked, while "Leads" gives the number of unique leads who clicked the link (see Email Link Performance Report - Marketo Docs - Product Docs).
- In the Email Performance Report, "Clicked Link" gives the number of email recipients who clicked a link the email (see Email Performance Report - Marketo Docs - Product Docs).
Hope that's helpful!