Are you certain you have your scaling factor correct?
Your Link and also https://www.bfs.de/DE/themen/ion/umwelt/luft-boden/spurenmes...
report ~50micro Becquerel/m3. Not sure how you calculated 10000 as the scaling factor.
Il a permis de détecter les retombées de Fukushima qui étaient environ 10000
fois supérieures à celles mesurées en janvier 2017 sur la France.Unfortunately, the BfS charts are updated weekly... Do they publish latest readings in raw format somewhere? I couldn't find anything other than the delayed raster chart.