Product notification question

I was out of stock on a few items for over a week, but added text to the product pages apologizing and urging customers to click on the product notification check if they would like to be notified when they were back in stock. I just sent out a "back in stock" product notification, checked the items I had been out of stock on, and Zen told me 4 notifications had been sent out. Does that mean 4 people wanted to be notified about these particular products, or were newsletter subscribers automatically included?

There are no automatic notifications.

Go to Admin -> Tools -> Newsletter and Product information

I think you will get the rest from there.

If you setup the email as a product notification email, then I don't think newsletter subscribers would (should) have received it.

To find out exactly how many customers have asked to be notified for each product, can I suggest the Products Notifications Report. I use it myself and find that it's quite helpful.