Since KOMPLETE (ULTIMATE) 8, the libraries employ a new file compression technology allowing for more high quality samples to fit into a much smaller package. In addition, all of the KONTAKT Library files have been saved in Monolith format, which further compresses the file sizes without any quality loss.
As a result, the KOMPLETE (ULTIMATE) 8 (or higher) libraries are smaller than their earlier equivalents, yet contain more instruments and samples. This results in a faster installation process and smaller file sizes while allowing for a much larger collection of sounds. On the package you may notice an uncompressed file size amount that is much higher than the size of your actual library. This is because the packaging was printed with the uncompressed library size which does not match your actual library file size.