def _on_ack_delivery(
        self, delivery: QuicDeliveryState, space: QuicPacketSpace, highest_acked: int
    ) -> None:
        """
        Callback when an ACK frame is acknowledged or lost.
        """
        if delivery == QuicDeliveryState.ACKED:
            space.ack_queue.subtract(0, highest_acked + 1)

        Callback when an ACK frame is acknowledged or lost.
        
src/aioquic/quic/connection.py