Questions about cart management backend

-- HikaShop version -- : 3.2.2
-- Joomla version -- : 3.8.3
-- PHP version -- : 5.6.33

Hi,

I'm puzzled about the cart management in the backend (in menu Customers)
Sometimes there are many carts in the listing with the same customer/IP address, with no or only a few minutes time difference. These customers are not logged in.

When I add a product to the cart myself, my cart is shown in the listing. And after that I add another product, and after that I delete a product. These changes are done in the original cart in the listing, not in a new cart.
That's the way it should be, I suppose.

So I wonder: why have some customers a few carts within a very short time? Should I change some configuration?

Details of the configuration: Multi carts are not enabled.
The cart retaining period is 12 hours; the frequency of the check is 12 hours.
Cachetime: 30 minutes (system cache conservative)

Regards,
Udo

Thanks, Nicolas.
I've disallowed /*updatecart/add* in robots.txt and now carts generated by search engines are gone.

A remark: why logging the temporary carts at all?
Perhaps it's useful for some shops, I wonder why.

Regards,
Udo