The photostream is the overview of all your images. The number of photostreaam views is the amount of times that someone has clicked on the "photostream" link (or your username). That is obviously going to be a different figure from those that have clicked on a specific image of yours. Not really that hard to understand if you think about it.
You are right, it was just me getting confused about how views were going through the roof for a certain image for a few days v the photostream views.
Anyway things seem to have quietened down now.