Calibration of measurement equipment to PN10 measures more particles than calibration to PN23. It is therefore logical that compliance with a limit when measured according to PN10 demonstrates compliance with the same limit according to PN23 but this text should be added for legal certainty.
FOD Mobiliteit en Vervoer/SPF Mobilité et Transports is the land, air, and water transportation administration of Belgium.
You can find more information about FOD Mobiliteit at their website.