These numbers refer to a queue of server requests that are waiting for the use of a native thread from the pool. The Work Queue Length is the current number of requests waiting for a native thread.
Peak is the highest number of requests that were ever queued up simultaneously for the use of a native thread since the server was started. This value can be viewed as the maximum concurrency for requests requiring a native thread.
Limit is the maximum number of requests that can be queued at one time to wait for a native thread, and is determined by the setting of NativePoolQueueSize.
You can modify the NativePoolQueueSize by:
Editing the NativePoolQueueSize parameter in magnus.conf
Entering or changing the value in the Queue Size field of the Native Thread Pool page in the Server Manager