...
Categorization and Grouping allow you to break the logged time down, based on users that logged time, projects, or Jira issue fields. The Categorize by, Group by, and Secondary Grouping together allow breaking down the data up to three levels.
...
In addition to this, you would also want to learn within each project, how much time was spent on bug fixing, new stories, and improvements. You could do that by additionally setting Group by to Issue type as shown. You can still see the total time spent per project, but you also get additional details on how does that look it looks for each issue type in the project.
...
In the same manner, you can break down the details preseneted presented by the Worklogs table to the third level. In our example, by setting Secondary grouping to Priority, we also learn for each project, and each issue type within those projects, how much time was spent on issues classified as high, medium, and low priority.
...