How Many People Subscribe to the Escape Pod Podcast?

Since one of my stories will be coming out soon in Escape Pod, I’ve been paying closer attention than I otherwise might to how many readers it has. The site has a “feedburner” bar that lists the number of readers, but that number fluctuates from about 4,000 to about 6,000, sometimes within a single day. Is there really that much turnover? Or is the number just wildly inaccurate? Anyone have any reliable estimate on how many people subscribe to Escape Pod?