Exchange rate in opening balance

Exchange rate in opening balance

Dear,

My base currency is AED, and in opening balance I want to put CNY (Rate:  1 AED = 1.66 CNY)
So the exchange rate shall be around 0.5995

But when I put 0.5995 into the exchange rate column, it just changes automatically to 1.0

Could you tell me how to solve this problem?