Policies can handle exceptions, as you saw in the previous example. But policies can also check the result that a method returns. In this case the policy checks the Status (this is a custom type) returned - HandleResult<Status>. A policy can handle any type of result, e.g. HandleResult<string>, HandleResult<HttpResponseMessage>, HandleResult<int>, etc.
In this example the policy retries the request up to three times if the result is not a Status.Success.