Hello, @lanxing,
1. That is because you have set the Site Width as 1440px from XStore >> Theme Settings >> General, I have removed it and it is showing like this now: https://postimg.cc/wyKpZZqF & https://postimg.cc/v4VMhGMD but it also has the impact on your site other pages as well.
So I reverted it back as it was.
So you can try it by yourself. Other than that option the possible way is Custom CSS for that particular page.
2. I have added the Custom CSS code to the page Custom CSS XStore setting and it resolved the issue.
https://postimg.cc/HcfFVyc2
https://postimg.cc/FkyCznQr
Regards 8Themes Team.