User find some products, which has button Notify my. Means, the product quantity in stock is 0. Buyer is clicking button, because they want to get email, when product already will be in stock. Such buyer will be assign in to the Waiting list.
You can check the Waiting list and order product according buyer wishes: Site > Control Panel > icon Freeshop > ikona Waiting list
You will see the product, user email, is he notified about new product quantity in the stock and notify date.
When you will change stock quantity, buyer will get email about possibility to buy the product. You can change the status in Waiting list by clicking the product name and change quantity in Product status tab.
Pay attention. If you see product quantity more than 0, means that the buyer wanted to buy more quantity than possible. You can contact and ask buyer about that.