Aggregation is a function that applies to the entries of a certain field. It allows you to see the function of your choice — Sum, Minimum, Maximum or Average value of a certain field. To add Aggregation to your Library, you need to choose it whether during the creation process or while Editing an existing Library:
- Click Aggregation, then press Add function to start. Click Edit to rearrange the existing functions.
- When adding a function, first you need to specify the type of a Function (Sum, Minimum, Maximum or Average).
- Choose a Field to apply this function to.
- Set a Prefix to define how this function will be shown to the end-user.
This is how Aggregation is displayed while browsing the Library (Average duration line):
You can Hide or Show aggregation anytime, just tap the 
icon and choose the required option.