I'm rather sorry but the authors: 
"from about 7.3 GB to 6.2 GB, nearly matching Microsoft's claim of a 2 GB reduction"
In the real world 7.3-6.2 = 1.1 GB
Is the author's "new math" equating "1.1" to "nearly match "2"???
A statement of "nearly halfing Microsofts claim of 2 GB" 
would be more correct in this case.