By default, the quantity restrictions apply to each product variation, that is if you set the minimum quantity to 10, the users will need to add to the cart 10 items for every variation. If you want to change this behavior and sum all the variations when calculating the quantity, you need to enable the option Unlock variation quantities that you can find in the tab General settings > Product restrictions.
You can override the global settings from the edit page of the variable product as follows:
– go to Minimum Maximum Quantity section and enable the option Exclude Product if you don’t want to apply any quantity restriction on the product, otherwise enable the options Override product restrictions and Enable variation restrictions.
-Now go to the Variations section, and set your restriction rules in every single variation.
You can set different quantity limits for each variation.