Foreign Exchange rate

Good day. I received an order from a foreign customer of 15000 USD. I charged him 1USD=90 BDT but now 1USD=110 BDT. When I create a sales invoice for the customer Foreign exchange gains (losses) show 32.48. How can I solve it?
I created foreign currency 1BDT=90 USD and at the time of creating the sales invoice, I set 1BDT=110 USD.

There is nothing to solve - has the customer paid you yet?

If the customer pays you 15,000 USD you will get more BDT than you expected

You seem to have confused the rate 1BDT = 110USD - is it not the other way round?

It seems you are wrong in determining the rates,

as you said in this paragraph

According to your manual calculations, what should be the value of this account?

Sorry I wrote wrong. Its actually 1USD=90BDT. According to me it should be like this:

Customer value in BDT 1,350,000.00 BDT
Charged to customer 15,000.00 USD
Paid by customer 1,650,000.00 BDT
Foreign exchange gains (losses) 300,000.00 BDT

Then your journal should like this

You need to check, how you enter your Transcation