Tira here, from Shopify Support.
I'm happy to take a look at this for you. I would like to ask a few questions to troubleshoot:
How did you cancel these orders? Check out our help doc on cancelling orders for an overview here: Cancelling Orders.
What payment provider are you using?
Can you take a screenshot of where your total sales is showing negative?
Once I hear from you I can take a further look. I look forward to chatting with you!