question about product code after copy a product

-- HikaShop version -- : 2.6.4
-- Joomla version -- : 3.6.5

Hello
I have a question about product code after copy a product
When i creat a new product and I left the product code empty after saving the system makes the product code, it is ok,
But If I copy a product when I open that I find the old product code+ copy+number, now If I delete that product code and I save the product the system doesn't make the new product code and it is empty.
It is normal??

Thanks
Frank

ok thanks