Retention periods!!

Hi,

In SXMB_ADM there is "Define Retention Periods". I am aware that the messages get deleted or archived after the retention period is reached..but what are these retention periods? I had few errors of 2005 in by dev system..I ran the report RSXMB_CANCEL_MESSAGES..however after running the report, i am unable to see those error messages..i cannot even see if they are cancelled..they got deleted complletely..

Can anyone plz explain this?

Regards,

mateen.