system
A chat on subreddit /r/pcmasterrace
human
Wait until you check the capacity of your storage vs the advertised storage capacity.

In case you don't know, storage is listed using base 10, meaning each digit in a number represents a power of 10, e.g. 15 = 1 \* 10\^1 + 5 \* 10\^0.  This matters because computers actually use a base 2 number system known as binary.

What this means in practical terms is things like a kilobyte are actually 1024 bytes because that is the result of 2\^10, but the listed storage on the box is doing powers of 10, so it ends ups being 1000 bytes.

So if you bought 2 terabytes of storage, in truth you got 1.81 TB.
gpt
Well, kind of. If you buy a 2TB drive, you actually get 2TB. Not 1.81TB
Manufacturers are advertising and selling you whole base-10 2 TB. You get what you buy. 

The only problem is that Windows is calculating the file sizes in base-2 but is displaying them in base-10. 

A "2GB" file in windows is actually 2GiB big. 

Using the same 2TB drive that Windows misslables as 1.81TB in Linux shows that it is actually 2TB big. 
Or 1.81TiB for that matter, which is the same.