Windows drive shows difference in used space and size of files available in disk

Today I face a weird issue where the total file size is less than  

Issue: I can see files including hidden files are consuming 32 GB  in C: drive whereas Disk C: is showing consuming 42 GB overall. I have verified  that recycle bin was also empty.

Luckily infrastructure team help me to understand the scenario. 

Root Cause: As per engineers, this is quite a common thing with Windows OS. Even when hidden files are set to unhidden, there will be files that won't get picked up and selecting all folders on the drive. 
Files that tend to remain hidden and don't get picked up are NTFS/ADS files, System restores files, amongst other system files.

                     As per them, there’s not too much that can be done about this, possibly could run a system clean-up but probably won't make a lot of difference. So in case you are struggling for space either add more space or try to remove error dumps.