Hi,
1. No. It would only be the case if the order status was first set to created before being set to confirm, and if the "update stock after confirm" setting of the HikaShop configuration is activated (otherwise, the stock is directly decremented when the order is created).
Normally, you're not supposed to confirm cancelled orders and thus it's up to you to change the stock if you want to as the system cannot know if that should be necessary or not in that case.
2. Could you do a screenshot of the settings of your report ? Could you provide an example explaining what was the original stock, what is the current stock, etc ?