Global [or App] Statistics are similar to Player Stats, except that they are stored centrally across all of an app's users.
Since global statistics are global to your app, they can be used to track sales, the number of total users completing certain tasks, global milestones, the number of users who joined a tournament, etc.
Creating a global statistic
Advance to the Design | Cloud Data | Global Statistics page, click the [+] button at the upper-right corner of the Global Statistics list.
With the Edit Global Statistic Rule window pop-up, fill out the fields that make sense to your app (Refer to the User Statistics page for the descriptions of each field.), then click Save.
Note that As same as the User Statistics, you can set your app to generate the Global Statistics dynamically at runtime from calling APIs of GlobalGameStatistics service.
Just simply select "Generate App Statistic Rule Enabled" on the Design | Core App Info | Advanced Settings page, and then call IncrementGlobalStats or ProcessStatistics to add new or update existing global statistics.
Note that using the [Force Synchronize] button to synchronize your app's Global Statistics list if some newly created Global Statistics from the API are not appearing on the list.
Implementing global statistics
Once your app's global statistics are created, you can use them associated with the gamification section, such as XP level, Achievements, Milestones, and Quests, for thresholds or rewards purposes.
Also as mentioned at the beginning, take advantage of the concurrency-safe incrementGlobalStats API, you can set your global statistics as counters to get the number of players for some type of event in your app.