Hai there, 

I wanna ask, how to make fixed quantity based on what my customer choose the option.

For example:

Product A has 2 size which is small size and big size.

For small size we will sell quantity for set such as 4,8,10 quantity

For big size we will sell quantity for set such as 12,14,16 quantity

So, if the customer choose small size, it will directly set the quantity for 4,8,10 dropdown option..

is there any plugin for this requirement? or how to do it on woocommerce..

Thanks.