Hi Nils,
Greetings from Syncfusion Support.
Currently we have displayed the week number based on the option ‘first day of the year’ which is the cause for the reported problem. We have already logged the feature request to include other options ‘first four day week of the year’ and ‘first full week of the year’ which can be tracked through the following link.
We will include this feature request in our upcoming volume 1, 2021 main release scheduled on March 2021 which will resolve your scenario. We would appreciate your patience until then.
Regards,
Nevitha