Unless otherwise specified, all currently-locked files in the default changelist will be unlocked.

Unlock files in changelist:

If you have more than one changelist pending when you run the Unlock command, a checkbox and a drop-down list of currently-pending changelists will appear. To unlock files within a specific changelist, activate the checkbox and use the drop-down menu to specify the desired changelist.

Unlock files in //client-path:

• ...and subdirectories:
  Files in the specified client path and all directories below will be unlocked.

  This is equivalent to the command line:
  p4 unlock //client-path/...

• ...at this level only:
  Only files in the specified client path will be unlocked. Any files in directories beneath the client path will remain locked.

  This is equivalent to the command line:
  p4 unlock //client-path/*

Selected Files:

If you have any locked files open in the current directory, you can specify whether or not to unlock them individually.

To include or exclude individual files from unlocking, click on the checkboxes for each file, and activate the radio button for the Selected Files option.