As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
PILOT REPORTS FILLING MAIN TANK THINKING IT IS FULL. AFTER A TIME GAUGES INDICATE LESS THAN FULL. INSPECTION OF INSIDE TANK THROUGH FILLER HOLE REVEALED DATA PLATE FROM FUEL PROBE COVERING THE FLANGE ASSY WHICH ALLOWS FUEL TO CROSSFEED TO OTHER TANK. REMOVED PLACARD, OPS NORMAL. RELAYED INFORMATION TO TECHNICIAN.