Hello MySup
Are you doing the migration yourself through the export to QuickBooks Online or has this been requested by the migrations team?The rounding is different in desktop in comparison to Online which could cause an issue or potentially if there are transactions which should not have been in the exchange differences account.
We would need to look at the account itself to see why this is happening. Can we ask in this instance if you can call our desktop team on 08081689535 and they can do a screen share to have a look at why this may be or alternatively we can request or migrations team to call you and they can do the transfer of the data and make sure the exchange rate differences account uploads correctly
If you want to go for the latter let us know we would just need the best time and date for a call
Emma