If you want a partition exactly 33 GB large and you don't get that when you choose 33 GB as partition size, then set it to either 33,792 mb or 34,603,008 kilobytes:
http://www.t1shopper.com/tools/calculate/file-size/result/?size=33&unit=gigabytesThe reason behind these odd numbers is that the computer uses not a decimal but an octal system, based on the number 8, not the number 10. This results in 1 GB not being 1000 mb, but 1024 mb; and 1 mb not being 100 kb, but 1024 kb, etc.
See this reference:
http://www.t1shopper.com/tools/calculate/
