https://www.td.gov.hk/en/transport_in_hong_kong/public_transport/taxi/taxi_fare_of_hong_kong/index.html (mirror) indicates that "Every piece of baggage (Except light personal hand baggage carried inside passenger compartment)" is charged 6 HKD charge when taking a taxi in Hong Kong.
What qualifies as a "light personal hand baggage carried inside passenger compartment"? E.g., does the regulation give any concrete numbers of the maximum dimension or weight for a baggage to qualify as a light personal hand baggage?
https://www.td.gov.hk/en/transport_in_hong_kong/public_transport/taxi/taxi_fare_of_hong_kong/index.html (mirror):