Ordering a product that has a minimum quantity

-- url of the page with the problem -- : christian-solishop.hts-france.org/boutiq.../champagnes-cremants
-- HikaShop version -- : 3.4.0
-- Joomla version -- : 3.8.8
-- PHP version -- : 5.6.36
-- Browser(s) name and version -- : Chrome 67.0.3396.87

Hello,

Due to the obsolete "add to cart system" becoming ... obsolete, I switched my website to the new add to cart system.

It's definitly better in lots of ways, but I now have a new issue, and don't understand how to fix it.

If I try to add to the cart a bottle of Cremant Blanc for example (which has a minimum quantity of 6 bottles), the button tries to add 1 bottle, thus displaying a pop-up saying 'Not enough quantity selected for the product Cremant Blanc "Perles de Lescure"'
With the obsolete add to cart system, this button would add the minimum quantity to the cart, and that's exactly what I need right now, but I can't stay with the obsolete version, considering all the bugs it's starting to have.

Hope the explanations make sense, if not I can give more details.

Thanks for everything you guys are doing!
Dani