The help indicates that a failed table will show -1 if the download fails. In my testing, the Record Count = 0 when a download fails.
Tested on version 6.2.1.17233 on this server - http://23.92.246.104/dsp/
The specific help page is: http://23.92.246.104/dsp/UserArea/FCBFA1C8-3BE7-4C42-B380-324A34CCF9D8/English/Documentation/index.htm#Workflow_Download_Failures_H.htm
This page could also be enhanced to indicate what causes records to be put on this page:
This content has been added to help.