Hi,
Thanks for the step by step ; but what is the link with HikaMarket ?
The only thing I see is that you edit the product in HikaMarket and not in the HikaShop backend ; but the way that HikaShop is handling variants quantity and the cart is only related to HikaShop and not HikaMarket.
So I'm afraid that I can't do anything in HikaMarket for your issue.
Regards,
Jerome - Obsidev.com
HikaMarket & HikaSerial developer / HikaShop core dev team.
Also helping the HikaShop support team when having some time or couldn't sleep.
By the way, do not send me private message, use the "contact us" form instead.