By default, the crawl speed for Site Audit is limited to 1 request per 2 second. 

However, for verified websites, you can speed up the crawl by increasing the number of parallel requests and/or reducing the delay time. 

The fastest you can set is one that does not impact normal users, so it depends on the response time of your website or how much load your server can handle. 

If you're using a host that is on the budget end (e.g shared VPNs), we recommend that you decrease the default values so it does not overload your server. 

If you're using a dedicated server, then you can increase the values to as much as you think your site can handle. If you're unsure what that is, a good load we can suggest is 6 parallel requests with a delay of 1 second.