Magento 2 – Get the original Qty on Qty change

I have a product for which another product needs to be added in the cart.

For this I need to check if the quantity of said product is changed in order to change the number of associated products.

I wrote a Plugin on the SetQty function in order to get this information:

    class ChangeQtyPlugin
{
    protected $checkoutSession;
    protected $cartRepository;
    protected $logger;

    public function __construct(
        Session $checkoutSession,
        CartRepositoryInterface $cartRepository,
        LoggerInterface $logger
    ) {
        $this->checkoutSession = $checkoutSession;
        $this->cartRepository  = $cartRepository;
        $this->logger    = $logger;
    }

    public function beforeSetQty(Item $subject, $result) : array
    {
        $oldQty   = $subject->getOrigData('qty');
        $addingQty   = $subject->getData('qty');
        $this->logger->info('testOld');
        $this->logger->info(print_r($oldQty, true));
        $this->logger->info('testNew');
        $this->logger->info(print_r($addingQty, true));

        return [$result];
    }
}

When I change the qty how, it returns:

[2021-10-11 12:52:51] main.INFO: testOld [] []

[2021-10-11 12:52:51] main.INFO: 10.0000 [] []

[2021-10-11 12:52:51] main.INFO: testNew [] []

[2021-10-11 12:52:51] main.INFO: 10.0000 [] []

Which is the New quantity.
How can I retrieve the old Qty before the change?