For documents in particular (since you mentioned uploading), this is likely because when you delete a document, this is a soft delete. Admins will continue to see the deleted content until you perform a hard delete via the Jive Admin Console. To hard delete, navigate to Spaces > Management > Document Management and then delete the document permanently to remove it permanently. Also, I'm presuming that you're viewing this from the Activity page as well.
For normal content (non-documents), there may be a delay between when deletion occurs and when the Recent Activity tile updates. I don't expect this should last more than a few minutes, at most.
Let me know if you have any other questions on this.