Metadata. Data about the data. Duration of the call. Location of the call. Time and date of the call. That is all metadata.
As I said, once they secure the data using one legitimate FISA approved warrant, they are under no obligation to delete or destroy the data when that one case is resolved. They can keep the data forever, and consult it at some later date for an entirely unrelated puropose, without having to have any court or judge approve it's use.
No, they also have megadata.