When the controls for the two units are physically located in one of the two units (e.g. control panel for a separate hob to be integrated in an oven), manufacturers should clarify how the measurement should be carried out (as mentioned in Annex III, Section 3 (b) (5)). In particular, manufacturers should describe the test setup.
Disclaimer: Please note that the European Commission cannot provide a legally binding interpretation of the EU legislation, as this is the sole competence of the European Court of Justice. Any remarks from the European Commission services are without prejudice to the position the Commission might take should related cases arise in a procedure before the Court of Justice.