T.code F-03 - clearing Open items

Dear Friends,

I do not  have authorization to T.code F-03

The user is facing the folowing problem.

I wanted to clear open balances in account 21000 that net to zero.

However, when I go into the function F-03 it is showing me a net balance of 20 CHF.

However, the exact same balances (they all have the assignment field Q2 2013) is showing a balance of Zero when I look at the account.

Clearly this is some sort of FX difference,  but both T-Codes have been run for the same date (23.08.2013) – do you know why I have a difference in my

Clearing Account?

Please suggest.

Regards

Sridhar