1TB (10**12) != 1 TiB (2**40)
My doubt was not for the size of the whole disk.
My doubt was that why is the maximum size of the root partition only 829 GiB when the other 2 partitions are 1024 MiB and 512 Mib, with the size of the entire disk being 930 GiB.
It seems I am losing around 100 GiB.
I am asking why am I losing so much space ?