eBay international standard delivery was the default. Can I use a Priority Regional box to ship?

[a.june]

I sold a 5 lb candle and it's shipping to Canada.

I always use Regional Priority Flat rates boxes but the ' Ebay International Standard Delivery' was pre filled.

Could I have used that Flat rate Regional box  or did I just waste  $5.00 to buy a Medium Flat rate box?

And, aside, I'm in the managed payment group and still trying to figure where the money is coming and going to. Waiting to get a refund on a 50.00 label is not a happy thought.

Any thoughts or experience with this?