Please divide 1000 billion by 1073741824. The result is going to be 931.322574… (my laptop's calculator app cannot display it entirely)
This comes from units. Windows uses power-of-2 units for showing disk sizes, while Linux (and ALSO the disk manufacturers) use decimal units. To Windows, 1kB is 1024 B while to Linux and the disk manufacturers 1kB is 1000 B.
The 1TB disk, if you look at its number of bytes, most likely has slightly MORE than 1TB, by perhaps 1MB or even more above that, probably due to internal organization as well as the fact that it must be a multiple of the sector size, probably half the Windows kilobyte (512 bytes, that is). It may have less than 512 bytes above the 1TB mark but most likely it's going to have a little bit above.
My 1TB disk has 931.39 GB according to the Windows disk manager, which is definitely a few tens of MB above the decimal 1TB mark. I'm pretty happy with it (except for the low performance; I needed the capacity so it's fine)