What ignusss said. If you only downloaded ~200MB of files with your preload, you didn't get everything that was available. That would just be the core game files (sufficient to play, but not everything).
Click that "+" icon beside the Gal Civ 2 listing in SDC, and you'll see that there are seperate listings for the Tutorials, Movies, and Multimedia. Downloading all of that brings the total size to over 1GB, and will mean you'll only have a few MB to get on the 21st.
- Ash