Your first screenshot shows Macintosh HD 'Logical Volume Group' (Gruppo volume logico) which is actually not a single drive, but a group of two combined, so that most of OS X sees it as one large, somewhat faster, drive.
The software/hardware that controls it, allocates most all of the space on both drives, and so Disk Utility reflects that.
The second screenshot is a logical partition (something that things can actually write to), and Disk Utility shows that there is space available.
Perhaps it's a bit like Apple reserving all the rooms in 2 hotels & allocating them as they like; so when you ask the hotel manager (the volume group) - all are taken.
Go to Apple reservations (logical partition), & they'll say there's plenty of space & put you (your data) somewhere suitable in one or both hotels.