This might seem a bit easy, but I have checked through the documents and checked "Delete archive after processing".
Yet, when Akeeba backs up, it retains a copy on the server; as well as places one into Amazon S3.
What setting is not checked probably, whereas to avoid having duplicates and only storing copies onto Amazon S3?
Here is a screenshot..
https://drive.google.com/file/d/1-n7qyrUMXec6vpHN9ppMClavQ_qwTo7d/view?usp=sharing
Thanks in advance...