Column width cannot be set in DataGrid Composite Columns

First of all, I am using translation software. I'm sorry if the context is wrong.

I'm using DataGrid Composite Columns, but the column width values are out of sync.
I am in trouble because the column width cannot be set normally.
Am I using it incorrectly?
If you make a mistake, please tell me how to use it.

We are not sure why column width is not working for you - not sure about the DataGrid header style however it seems that you are using a customized theme. Similar setup on our demo works normally:

Thank you for your reply.
I'm sorry the theme is changed with CSS.
However, the situation is the same if you do not change it.

I checked the demo again, but I think that the column width of the demo is different from the setting.
The Postal Code column is different from the value specified by Width.

Actually the width of the table elements is exactly what is specified:

You can check also this thread for reference:

Thank you for sharing the information.
I recently started using Blazor, so I'm studying.

I made the following confirmations.
Are you using this behavior?

①Change the column width of the last column

②Column width of "Country" column changes

This is not something limited to Blazor, it’s how HTML table works.

Thank you very much.
Check the code again.