You mean the "Free space 748,000,000,000 bytes 696 GB?
1 human GB = 1X10^12 bytes or 1,000,000,000,000
1 computer GB = 1X2^30 or 1,073,741,824 bytes.
Manufacturer's use human gigabytes because that makes their hard drives look a little bigger. Then computers use "computer gigabytes" and you wonder where all the space went.