Air ticket with confirmed date of flight and seat for a third country (region) traveling within 144

Hello! Can you tell me please what way i can prove "Confirmed seat". I and my family will come to Shanghai from Helsinki and in four days we are going to leave Shanghai for Hong Kong. I have payed and confirm tickets (i can print it) and confirmed seats but i can't show the immigration officer any paper proof of my seats confirmation except printed copy of Airline company answer from chat . What can I do? Thank you for your answer...