Dear Cyberpanel,
We installed well Wordpress at sub-directory:https://www.ledlight.net.cn/strip/
You See, When Backup, What Can I choose is website of https://www.ledlight.net.cn/ , not https://www.ledlight.net.cn/strip/
About Full Backup, How to Only Backup and restore Sub-Directory Website https://www.ledlight.net.cn/strip/ ?
Thanks
The best way to backup is to login file manager, navigate to the sub folder => Zip all file => Download it.
Then, come to the database, login PHPmyAdmin and choose the database of that subdomain, export it.
All is done!