Your data
The Data page in the rail lists every dataset you have imported.
Each row shows the symbol and name, the dates it covers, the number of one-minute bars, any gaps found when it was imported, its size on disk, and the sessions that use it. The Clock drop-down sets which time zone its times are in, the same setting as in Data and the clock.
Deleting a dataset
Delete asks first, then removes the dataset and its prepared timeframes from this computer. A dataset that a session uses, as its main instrument or one of its others, cannot be deleted: delete those sessions first, or keep it. To get the data back later, import the file again.