As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ATB - C SYS HYD QTY LIGHT FOLLOWED BY C SYS HYD PRESSURE EICAS MESSAGE. DECLARED EMERGENCY AND RETURNED TO DEPARTURE. FOUND RT LCCA FILTER COVER PACKING BROKEN. REPLACED PACKING AND LEAK CHECK OK. SERVICE RESERVOIR TO FULL. REF IPC 27-11-14-03, ITEM 140.