Getting a 10GB Minimum error when trying to do a windows partition, have 20GB free on my 64GB SSD.
Its likely there isn't enough contiguous space for it to create the partition... ie. a full chunk of empty free space. Should have created the partition sooner before loading it up with other stuff on the OSX side. Not sure if there's some workaround that might work - maybe copy your mac partition to an external USB drive with Carbon Copy Closer, reinstall OSX, do Bootcamp, then boot from the external USB drive and clone back the OSX files?
Someone will probably recommend a defrag tool but the free solution is to backup your drive then format your drive then restore with Time Machine or do a fresh install. I had the same problem on one of my Macs a couple of years ago and a clean install fixed it.