si vs binary units

https://alpha-wiki.win/index.php/Understanding_IEC_Binary_Units:_A_Practical_Guide_for_Data_Storage

If you've ever wondered why your 500 GB hard drive shows up as 465 GB on your computer, you've run into the difference between SI and binary units. SI units (like gigabytes) are based on powers of 1000, while binary units (gibibytes or GiB) are based on powers of 1024, so drives marketed in SI or decimal units have less space in the binary counting systems computers use.