Oracle Autonomous Database - check used storage space

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Hello. I recently noticed that my Autonomous Database is running out of free storage space. This is strange since I store a small amount of data in it.

Checking the Database Dashboards gave the following result:

Also, to check the space used, I ran the query:

SELECT NVL(OWNER, '--TOTAL--') as OWNER, SUM(BYTES)/1024/1024/1024 as SIZE_GB

FROM DBA_EXTENTS

GROUP BY ROLLUP(OWNER)

ORDER BY 2 DESC;

If we exclude SSB, then the used space will take up approximately 5.5 GB, which coincides with the data of the "Storage Used" dashboard.

Why is the Storage allocated 14 GB in this case?