Hi Angie,
Sorry for the delay in reply.
The number of subscribers may not be equal to the number of people who have listened to the podcast. It only shows you how many people are using feed readers to read your podcast. Those people may be notified by their feed readers when your podcast has new items.
To know how many people listening to the podcast, you need to track item enclosure downloads (podcast downloads). This service is not turned on by default, however, you can enable this option in "Analyze" ---> "StandardStats".
The following page will give you more information about StandardStats:
http://www.feedburner.com/fb/a/publishers/standardstats
Hope this helps.