There's a simple rule you can follow -- if you don't know whether to delete a file, then don't.

When you scan one or more drives for duplicate files, it lists all the duplicate files found on the selected drive(s). This does not necessarily means you can delete all of them, since sometimes it is normal to have duplicate files (for example the Windows Sysbckup Directory). It's up to you to decide which ones are needed and which ones can be deleted/moved.

When you can delete duplicate files is when they are exactly the same size, have exactly the same name and exactly the same date. Even then, don't delete the duplicate at first. Backup it using the build in option of System Cleaner instead. If your system runs fine for a few days, then delete it.