Grid view when I press the home button appears with 2 columns instead of 3 in the first row

I setup in the (Posts) Grid Layout to show 3 rows and it is working fine like at

https://www.nexusbr.com/pt_br/blog

The problem is when I open a post and select the home button. Then the first post is with a black background, like at

https://www.nexusbr.com/pt_br/blog-inovacao-saneamento

How do I setup to show 3 columns in the first row, without this black background?

Thanks.