*now we all know that is wrong*
The ISO definition of a GigaByte is 1,000,000,000 bytes - so far from being wrong, they are in fact correct.
What we do (or should ) all know, is that computers in some respects have an alternative definition for kilo - instead of 1,000 is 1,024. Nowhere else in tge real workd is such useage "correct" or even appropriate. This is merely a quirk resulting from a shorthand method for expressing binary numbers in decimal.
MS have done the wholly correct thing here and defined exactly which numbering convention the are using - as they do when you look at the properties for disk drive capacity in Windows, too. This means you are not in any doubt at all about how much storage you are getting.