Why there are two payment for one order with same remote ID
For some reason the IPN for that payment triggered the creation of a second payment transaction within Drupal Commerce. Couldn't tell you exactly why it happened, though it could've been the result the customer's page request and the IPN request being processed simultaneously. The module ought to filter out IPNs to not duplicate transactions like this, so if you see it again, file a bug report in the module's issue queue.

To answer your direct questions, the order cost $17, the balance is now negative (meaning it appears overpaid within Drupal Commerce, even though it wasn't), and it would be safe to delete one of the transactions (but you'd need to be logged in as an administrator).