Volume compression sub-byte

I have a 8.78G documents

like to reduce the volume to a 3-4 compressed file.

I would like to ask how to fill in for each of the compressed file is the number of bytes it! !

sub-volume compression

to right-click the compressed file, click Add to the compressed file …

in the sub-volume compression file size, you can choose, Note:If you do not want the size, can be entered into the

would like to reduce the size of the volume, such as:400m, can be determined.right To blow compressed files – click to add files, the “sub-volume compression file size, bytes” input, such as:2000M