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.
The German Aerospace Center (DLR) is the national aeronautics and space research centre of the Federal Republic of Germany.
You can find more information about DLR at their website.