Hello, take a closer look at the coloring again, it seems to me as if he colored a small part blue in the middle of the 6. You can see it in the picture below.
I’m not entirely sure if this could help if you played around with it.
Bambu Wiki - Variable Layer Height
It may be that your object does not work well with the 0.20 height because the height of your object is not ideal for the slicer if you want to print in 0.20.
I don’t know if it’s an option for you, but you might want to test how it behaves if you make the 6 a little less deep, around 0.10, and then see what happens.
Those would be my first approaches to what I would try to solve the problem.
Sorry for the bad English (worked with translated)