payment journal issue

my issue is rounding value appear and also loss and gain lines appear with the same value , although exchange rate in invoice ,payment and clear are the same value 6.03.and the issue in details is :
1- i have an invoice with exchange reate 6.03
2-pay this invoice with the same exchange reate
3- clear the payment with the same exchange rate
but in the journal
rounding line appear with a big value.
and loss and gain lines appear with the same value.

i think the problem is in setup but how i fix it ?