If we ever notice similar transactions in your account, we'll list them under "Resolve Possible Duplicates" in red under Troubleshooting on your Transactions dashboard. Click that link to view what we consider to be possible duplicates, and let us know which ones you want to keep and delete. If you're not sure, you can mark it as "Unknown" and come back to it later.
We pick out possible duplicates by date, amount, and transaction title. It's possible that you may have just had 2 or more of the exact transaction in the same amount happen on the same day. In that case, mark all to "keep". Otherwise, delete what shouldn't be there then click the "Resolve Duplication" button to keep your books in order!