This 10% figure seems to originate on this blog post: http://greatergreaterwashington.org/post/19848/musks-hyperlo...

The guy makes assumption of single 28 person pod leaving every 30 second to get 3360 passengers/hour throughput. But these parameters are not set in stone. Pods could be joined into platoons that move together to form "trains". With 10 pod platoon you get 33600 passenger/hour -- neary 3x throughput of California High Speed rail when it's built. Pods could also be made wider to accommodate multiple people along cross-section.