It automatically shrinks every photo of folder and creates an identical shrinked version of it which exactly takes space you decided on disk.
Choose your source folder to shrink. Then analyse it to start shrink process.
Pull down slider to set the shrink size. You can shrink to any size.
Choose destination folder to store your new shrinked folder. Then just press Shrink button to shrink your folder. It will show you all process while shrinking.