Hi Sean,
On a +ve note, I observe that if you save this customized canned report(which lists only the last 30 days of xfer statistics) as a OCUM 'custom report', it retains this characteristic (filter setting) whenever you run it later.
If you've attached a say weekly schedule to this custom report, you'd have to manually alter the custom report from-time each time and unfortunately I see no facility to automate this here.
OCUM uses Actuate BIRT reporting engine at backend to provide this facility and this is a limitation from BIRT looks like.
regards,
Kiran.