FusionReactor tracks the timing from when the request enters the servlet engine, up until the last byte was sent from the server. In this case, that would be the [x] ms you are seeing from FusionReactor.

On the other hand, your browser tracks the time from when the initial request to the server is sent, until the data in the browser has been fully rendered. This would be the reason why your browse is showing up as the request taking

[y] ms.

However, it is possible to track the request on the client through FusionReactor. If you track this information you should see that the entire request from server to client took approximately [x] seconds.

You can do this using the User Experience Monitor.