As mentioned in this blog post http://developers.facebook.com/blog/post/464/
....enable “Upgrade to Requests 2.0” in your Developer App settings on the “Advanced” tab. This switch controls the bookmark counts seen by your users and synchronizes the count with sent requests.
I have thoroughly checked the "Advanced" tab in my application settings, but I couldn't find any such "upgrade to requests 2.0" option.
You clearly created application after September 2011. Since then this option is no longer available to newly created applications.
According to Completed changes list:
January 1, 2012
All apps will be opted into "Upgrade to Requests 2.0" and "Requests 2.0 Efficient" Migrations Existing apps will be opted into “Requests 2.0 Efficient” and "Upgrade to Requests 2.0" migrations and all developers must ensure that they are using the correct request_id format and deleting requests appropriately. Details here.
Also Improvements to Requests 2.0 blog post (from September 30, 2011) states:
Starting today new apps will automatically be opted into “Upgrade to Requests 2.0” and “Requests 2.0 Efficient” and these migrations will no longer be available in the app settings for new apps. This requires developers to use the new
request_idformat as detailed above. In addition when a user is directed to your app, by clicking a Request from the app, the games dashboard, or from a Request notification, you must delete the request after it has been accepted. These are not automatically deleted once they have been clicked, thus it is the developer's responsibility to clear them once they have been consumed. See sample above for how you can delete these requests.