The Oracle database is made up of 20GB data files. These are created as the database accumulates acquired data. The limit is set to 200 data files, of which about 150-180 are for UNIFI.
When you delete data, some of these files are emptied, but the 20GB file remains ready to contain new data.
For this reason, the database cannot "shrink"; it can only increase until it reaches 200 data files or the drive space is exhausted.
It often helps to use the analogy of a bucket of water. If I empty half of the water the bucket does not get smaller. The same is true for the UNIFI database—it will still take the same space on the 4TB drive of the workstation.