You can only have 3 or 4 maps. You need to edit that down to fit. The file sizes listed for the files are compressed (zipped) sizes, when the files expand they are about 1.5 times the size. Also, you need to leave 1,5 GB free for processing space.
See this tutorial: Tutorial: Current EU Maps Installation on US Imported Vehicles - Ford / Guides & Info - CyanLabs Official Community
Selecting Files for Installation