32GB = approximately 28GB-30GB
64GB = approximately 56GB-60GB
128GB = approximately 112GB-120GB
256GB = approximately 225GB-238GB

512GB = approximately 450GB-480GB
This is calculation difference between manufacturer and your PC, please Google 'USB FIASH DRIVE capacity' to get more information.
Your PC says 1GB = 1.073741824 Billion bytes where Market Defines 1GB = 1.00 Billion bytes.

Note:

Speed based on internal testing. Actual performance may be lower depending on the device, interface, usage conditions and other factors.
1MB=1,000,000 bytes. 1GB=1,000,000,000 bytes. Actual user storage less.
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2. All products are in line with Sandisk official website.
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Package

1*SanDisk USB Flash Drive(with retail package)