You definitively want to read up about HANA Administration... I could recommend a well received book for this case 
Anyhow, just like nearly any other DBMS SAP HANA doesn't allocate space on disk table by table, but rather in a bulk fashion. When you delete data it will not give the space back to the file system but keep it allocated for further reuse.
You might "reorganize"/"shrink" your data files via the ALTER SYSTEM command, but actually that's not what you want to do in your case.
Looking at your screen shot I'd guess that you are looking at the effect discussed hereThe $delta$ container is not releasing space
So check if SAP note 2144274 applies to your system.
- Lars