https://www.seagate.com/jp/ja/support/kb/why-does-my-hard-drive-report-less-capacity-than-indicated-on-the-drives-label-172191en/
1TB (1,000GB) 931GB
2TB (2,000GB) 1.81TB
3TB (3,000GB) 2.72TB
4TB (4,000GB) 3.63TB
5TB (5,000GB) 4.54TB
6TB (6,000GB) 5.45TB
8TB (8,000GB) 7.27TB
10TB (10,000GB) 9.09TB
12TB (12,000GB) 10.91TB
14TB (14,000GB) 12.73TB
16TB (16,000GB) 14.55TB
18TB (18,000GB) 16.37TB
20TB (20,000GB) 18.18TB
