There is no command to shrink a data device, and no other safe, supported way.
If you have not yet extended your database on that device so it uses the huge amount of space you can follow these steps:
- make sure you write down in what order your database has been created on the devices (i.e. data, log, data, data, log) so you can recreate the database in the exact same order.
- backup your database
- drop your database
- drop the device that is too big and recreate it with the normal/previous size
- recreate your database according to the script/specifications you wrote down in step 1
- load the dump
I'm not crazy, I'm an aeroplane!