RSTBPDEL is a standard Executable ABAP Report available within your SAP system (depending on your version and release level). This report deletes change documents from the table log database. if you are facing issue while deleting the table logs (job completed successfully but no reduction in DB or table logs) as per SAP note – 2388295 – RSTBPDEL | Delete logs periodically.
SAP released another note for resolving this issue – 2634844 – Deletion program RSTBPDEL not deleting data of table logs.
This note need to implement via SNOTE in all the impacted systems & this will also introduce a new authorization object. Once SAP note has been implemented re trigger the job again & see the difference now.