From the Admin application, go to Advanced > Data > Datasets.
The Datasets page shows information for Datasets and Snapshot such as the following:
Total storage size used by all stored Datasets/Snapshots.
The size of all storage used by Datasets/Snapshots marked for deletion.
A table of all Datasets/Snapshots from the history of the deployment. You can sort the table by status, size, and the name of the containing Project/Dataset.