On pages that contain circuit availability data such as the IP Access Detailed View: http://test-msr.geant.net:8888/msr/ms_ip_avail_new.jsp There is a column for the Total Outage Time During Maintenances.
UPDATE reports.report_service_availability
SET out_maint = '06:00:00'
WHERE base_absid = 31467
AND year = 2017
AND month = 7;