Limit of posts on home page

HI. I want to have of my latest posts show on my home page. FOr some reason, I cannot have more than 6. Posts that I want to have appear on the home page are being sent into the “older posts” category. Any way I can keep 9 posts on the home page?

You can take a look at my site here to see the porblem: https://www.sciencevisualization.com