Contributions show you a single commiter performance over the last year. Unlike other Awesome Graphs stats, it's located right in the Stash user profile. So you'll need to enter a user's profile and click the Contributions tab. 

You'll see the user's calendar, it comprises all days over the last year starting from the current date. Days when commits were made are green. days without commits are grey. You can hover a mouse over a day to see how many contributions were made on it.

Click a day for a detailed list of commits made on it, below you'll see JIRA issues fixed by these commits.