The Dosimetry Service is applying the legal recommendations for dose calculation in Switzerland. The 2004 recommendation (original pdf document only available in German​) of the Swiss Federal Commission on Radiation Protection states that all monthly doses below 75 µ​Sv (=0.075 mSv) should be rounded to 0 when transmitted to the authorities. Why is this so ? At CERN we are using a very accurate dosimeter: the DIS-1. It has a detection limit down to 1 µ​Sv whereas most of all other dosimetry services in Switzerland are using other detection techniques that have a detection limit of 50 µ​Sv. Below this threshold they cannot tell if there is a dose or not. One can thus understand that CERN should not be reporting doses that the other dosimeter cannot 'see'. The second reason is that the background is highly fluctuating in Switzerland depending on your location. If someone is in a region with a high background he will record higher monthly dose than in low background regions. But this dose is coming from natural radiation, it should not be taken into account as a real dose for workers. This is why the experts have fixed this limit at 75 µ​Sv. In practical if you read a dose below 0.08 mSv on the reader your official monthly dose will thus be 0 mSv.