How to prepare Managed Meta Data for Highlighted Content Webpart?

Hello,

I played around with the Highlighted Content Web Part and I am really confused, cause the web part is not displaying what I expected.

As you can see, I have a lot of items, where the value of my "TestColumn" is "true":

My pages are located in a subfolder of the site pages library.

I created a managed property called "TestColumn":

Now, when I use the Highlighted Content Web Part I get the following result:

I only get a result of three items.

I configured the web part as follows:

It would be great if you can give me a tip about what is wrong with my configuration.

Thanks in advance. :-)