Logical Volume Group "Available Space"
You may be [not] seeing the other partitions on the drive, Recovery &amp; EFI, which will be contributing to that 'extra' space.

Try enabling the debug menu in Disk Utility, then enabling all partition view…


Quit Disk Utility
Open the Terminal utility
Run the following Command:
defaults write com.apple.DiskUtility DUDebugMenuEnabled 1
Relaunch Disk Utility
In the new Debug menu, enable 'Show every partition'
check if EFI &amp; Recovery add up to the 'missing' space
For me, EFI is tiny, approx 200MB, but Recovery is approx 1.2GB
I don't have an LVG, so there may be a 4th partition governing that.