This panel gives you an overview of how many pages have been optimized by NitroPack.

You can also see when the last cache purge occurred, along with the reason for the last purge.
Clicking the number of optimizations gives you a breakdown of the number of cached pages for every page type - mobile, tablet, and desktop.

You can use the Purge Cache button to purge your entire site cache.

On the other hand, if you want to clear the cache for a specific page (or pages), please refer to this article.