When you return an item to a merchant in person or online, your refund will be processed by the merchant and sent back to your card. These can take 7-10 business days to appear back in your Current account, depending on how fast the merchant processes them.
A canceled transaction like an Uber ride or pending Amazon order will result in an authorization hold on your card from the merchant. These generally take 7-10 business days to expire from the authorizing merchant as well.