Mavericks performs some advanced timer coalescing to reduce power consumption. Apple claims up to a 72% reduction in CPU activity. I think (but am still searching for written proof) that Idle Wake Ups
is the number of times the CPU leaves the idle-state per quanta of time. I'm not sure what that quanta is (probably one second).
You can read more about Maverick's power savings at Ars Technica's excellent review of OSX 10.9 (page 12, "Energy Savings").