Downlink get wrong freq like 485.3MHz in CN470

When the end-node sent joinrequest in 485.3MHz,then the APP sever receives the reques and sent a joinaccept msg.But the donwlink freq is same with uplink’s in 485.3.All devices are normal running on TTN server,and the donwlink freq is 505.7MHz.Is my setting wrong?

This is the TTN downlink packet.