Installed WordPress Location

Basically yes, but you’ll have to ensure that your sub-domain’s document root set to the correct file location so that it picks up your WordPress files correctly.

Then you’ll have the WordPress Site URL, which I assume would be:
mydomain.com

Then you have the WordPress URL, which would be your sub-domain. You’ll just need to ensure your sub-domain points to the right place on disk.

But actually, you’ll find when you do this that you’ll be able to access the admin for your WordPress site from your main domain as well. No stopping that really with this configuration.