Well, in reality, not all of that 1.6 GB is the software. It's largely drive manufacturers lying to you:

22(fake)GB =
22,000,000,000B =
22,000,000,000B * 1kB/1024B * 1MB/1024kB * 1GB/1024MB =
22,000,000,000B * 1GB/1,073,741,824B =
20.489(real)GB
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Bitt Faulk