Check in baggage at Shenzhen Shekou Port only 1 piece of luggage free of charge.

Can someone guide me to the correct website for details, or elaborate how this works?

I'll be taking a ferry from Shekou, and then a United airline flight to Singapore. I will have 2 check-in luggages and 2 handcarry bags. I heard that I'd have to pay rmb30 for 2nd piece of luggage?

Thanks much