A job can be setup with std_out_file / std_err_file attribute. These files reside on the Agent. AutoSys's default retention period for job runs is 7 days. Agent's folder containing std_out_file/std_err_file could have much older files than 7 days.
Environment
Workload Automation AutoSys
Resolution
AutoSys archive events process archives job run info in AutoSys. Default retention for this is 7 days.
That's the reason why only those job runs can be seen via AutoSys / WCC(WebUI)
Agent has configurable settings for joblog / spool cleanup, but those settings allow clean up of any *joblog / spool files created in the Agent's Spool folder
Agent does not clean up std_out_file / std_err_file referenced files, because, that set of data created by jobs could be further used by some other down the road jobs or applications that AutoSys has no control over
Such std_out_file / std_err_file need to be maintained outside of AutoSys by application teams