AQT behaves in the following way:
alter session set NLS_NUMERIC_CHARACTERS=',.'
To further complicate matters, most databases do not recognise a comma Decimal Separator in numeric literals.
This means: if you are specifying a numeric value in a Where clause, you must specify it with a fullstop, irrespective of what you have set as your Windows Decimal Seperator. The same applies for numeric values coded in Insert and Update statements.
AQT helps you use the correct format for a numeric literals; when you use List Values to display the values of a numeric column, AQT will display it using a fullstop instead of a comma. Similarly, when you go into Update Mode, AQT will automatically change all your numeric values to have a fullstop. These features will ensure that your numeric literals will be specified in the correct format.