Requirements to import min max quantities
You need the custom fields add-on and in the settings tab you must add these fields
group_of_quantity, maximum_allowed_quantity, minimum_allowed_quantity, minmax_cart_exclude, minmax_category_group_of_exclude, minmax_do_not_count to the custom fields. When you have done this, the fields will be available in the header page. If you use the same names in your CSV, the fields will be automatically mapped for you when creating a header.
Group_of_quantity, maximum_allowed_quantity, minimum_allowed_quantity should be integers and minmax_cart_exclude, minmax_category_group_of_exclude, minmax_do_not_count should hold the values “yes” or “no”.
Description from Woothemes
This neat little extension allows you to define minimum/maximum thresholds and multiple/group amounts per product (including variations) to restrict the quantities of items which can be purchased.