The author stats page is accessed by clicking the icon next to a repository. This page shows stats for every author contributing to the repo, as opposed to statistics for all authors put together.
Links beside each authors name are versions of tools available for the repository itself, but constrained to show data for that particular author.
Of particular interest is the graph icon next to an author name - it shows the graphs of all work the author has done across all repositories in the organization within the selected date range - which is a great way to see what features a given individual is working on. In most corporate contexts, it is quote common for developers to hop between multiple repos, and the graphs can easily track decades worth of history.
Clicking on the chart icon beside a particular author will load the stats for that author across all repositories within the organization.