Time taken to execute query seems longer than time measured in query...?
The elapsed time measured by the T-SQL batch will include only execution time. 

The elapsed time measured by the client application will include not only execution time but also compilation time and network latency.

Run your batch with SET STATISTICS TIME ON to see if the unaccounted time is due to compilation. With SSMS, you can also include more detailed client statistics (Query-->Include Client Statistics ).