Paxos later announced that the mint was an "internal technical error", and that they had burned the excess tokens.
While PayPal promises its customers that "Reserves are held 100% in US dollar deposits, US treasuries and cash equivalents – meaning that customer funds are available for 1:1 redemption with Paxos," there clearly isn't much in the way of safeguards to ensure that is always the case. As with most stablecoin issuers, Paxos merely issues self-reported and unreviewed portfolio reports, and monthly third-party attestations (not audits) of reserves.