Tolerance during voucher match

Hi Experts

In this case if tolerance on Amount is set to 10, if the PO Amount is 100, During Voucher match if PO Amount is greater than 110, “Value Exceeds Tolerance” will be shown

But my concern co base currency  in the PO is gbp & exchange rate is  395 and  receipt also done in 395 however during voucher 436.92

and i am getting the error of tolerance and that to in the converted amount ..

any special calculation as the rates are different ??

Thanks

Divya