The number of requests that were rejected because per-application queue limit was exceeded
This value may grow if an application is overloaded because of a large number of requests. It may also represent requests that are waiting on other services to respond or software errors resulting in no response being returned.
If the traffic volume is overloading the server, reduce traffic by adding additional servers to the pool. If the issue is caused by another system or a software error, restart the website and report the problem to Microsoft.