If you find you need additional space for a database device¾and if there is adequate space on the storage media¾you can expand the space allocated to that device.
The Size (MB) box displays the current size of that device.
A database device can be enlarged using this technique, but it cannot be shrunk.
You can also use the DISK RESIZE statement to increase the size of a database device. For information about the DISK RESIZE statement, see the Microsoft SQL Server Transact-SQL Reference.