Adding extra luggage (china southern airlines)

Hi everyone,

I booked a flight with China Southern Airlines: Chengdu → Guangzhou → Amsterdam (one booking, one PNR). Each ticket includes 1 piece of checked baggage, 23 kg per person.

I want to add extra baggage through the app of China Southern, but it shows that I need to pay for both segments. If I add it for both, the total comes to €500 for 2 people, which seems really high.

My question:

Do I really need to pay per segment, even though Guangzhou is just a layover and we don’t pick up our bags there? Or can I just purchase extra baggage for the Guangzhou → Amsterdam segment?