Your two credit cards of China CITIC Bank share the credit line. That is to say, your first card is 5000, your second card is 5000 and your third card is 5000. The available limit of three cards is only 5000, not 15000. Your first card cost 1000, so the remaining limit is 4000, and your other CITIC cards only have 4000.

Now many banks attract investment by sharing quotas. Industry and commerce. etc