Values ​​exported from Financial Reporting Studio to Excel with the wrong sign!

We configured a report on FRS (Financial Reporting Studio), the customer asked us to set the opposite sign on the values ​​present in the system (e.g. in the system the value "X debit" is with a positive sign, the customer asked us to transform the value with a negative sign).

Unfortunately when we export the report to Microsoft Excel the situation changes, that is, the value at sight is correct (with a modified sign and therefore negative) but inside the cell the value is with the original sign (therefore positive). See the screenshots

We should find a way to ensure that the signs are always correct even when exporting to Microsoft Excel.