Maybe I'm being dense, but could someone kindly explain to me the "Web App" example on that Sprites page?

"30 hours of wake time per month (~5 concurrent users avg), averaging 10% of 2 CPUs and 1 GB RAM"

Does that mean it would sit available but using 0% when there's nobody on the site, and just bill for usage when web traffic is causing the server to do work? So if the web app went a month with no visitors it would cost nothing (except for the file storage fees)?