Did you refresh the data?
Is the time range of your report different?
There are a lot of threads on the details of Email Perf vs. Campaign vs. Smart List counts.
The Email tab of the Smart Campaign is basically a little Email Performance report. The lead column in the Email Performance reports counts total unique leads who clicked a link in your email. The Email Link Performance report leads column total is not unique leads, which is why the number can be higher than the number on the email performance report. Leads can be counted twice in the Email Link Performance report if they click on more than one link.