The SLA feature allows you to regularly test the capabilities of your backend.
It allows you to see over time whether your backend server is responding correctly, so that you can offer the best possible quality of access to your Web pages.
When you create a site rule, only the / index page is tested.
The reverse proxy is not able to check the pages that are critical on your website.
The more URLs you specify, the more the reverse-proxy will be able to tell you the availability rate of your backends.