Firstly, the complete CSD System 2020 downloads should all be approximately 9.0 GB in size. If your download is significantly less that this then you should attempt to re-download the installer package. See the following support database entry for help with downloading.
On Windows systems we have had reports of the built-in zip functionality of Windows being unable to unpack the contents properly, particularly the large 'dist' file. In this case we would recommend downloading and installing a zip utility, such as 7zip.
Each CSDS download can be verified by comparison of its MD5 checksum with those listed in the 'CSDS & CrossMiner Download MD5 Validation Checksums' file provided with your download links. This file also contains instructions on how to obtain an MD5 checksum on our supported platforms.