It applies to all places where the amount is present (frontend and backend also).
For example, see the screenshot.
For demonstration: The green-marked amount should have the following format correctly:
- 100.000,00 Kč
- 100.000 Kč
- 100 000,00 Kč
- 100 000 Kč
Generally, the numeric format in most European countries (and many others) is 1.000.000,00