Describe the first visible overflow, not just the wet patch.
Notice which edge spills and whether water appears at a corner or beside a pipe. If it only happens during heavier rain, include that observation. A mark on the lower roof may be downstream from the visible gutter, so avoid deciding the fault from the mark alone. Tell us about previous clearance, known damage or a recent change to the building. A leaking joint and accumulated debris need different next steps.
An addition can have a shorter channel and a different outlet from the main house. Give that section its own label in photographs. This helps include the lower gutter you want cleared even when the main overflow concern is higher on the building.