Disk Inspector displays list of volumes presented in system. For every volume displays its free size and total size.
At the bottom of volumes list there is a panel with detail volume information. Toggle panel state using ⌘+V shortcut.
Disk Inspector displays volumes of types: Hard Drive volumes, Flash Drive Volumes, CD & DVD disks, external storage disks. All volumes being displayed are grouped by type.
If a volume is mounted or unmounted in your Mac, Disk Inspector handles the system notification and refreshes list of volumes. Nevertheless it is not recommended to eject or unmount disk during scanning process.