Defrag does not change the amount of Disk Space. It neither increases or decreases space used or free. Windows Defrag runs every three days and optimises program and system startup loading. This is not controllable.
Can you tell me more about defragging?
Defragmentation is the process of locating the noncontiguous fragments of data into which a computer file may be divided as it is stored on a hard disk, and rearranging the fragments and restoring them into fewer fragments or into the whole file.