Hi Stacey,
Could it be possible, that the children of the Feature and/or other scheduled items for this Milestone are either in closed projects, or in projects, that you do not have permission for?
The count would still be the complete number, as those workproducts have not been removed, but they just might not be accessible for you.
For the feature, you should be able to check in the revision history of the feature to see, if any children have been added and/or removed.