Cart total min/max quantity – will check minimum and/or maximum quantity for all products in cart (i.e. sum of all quantities).
Per item quantity – will check minimum and/or maximum quantity for each product in cart. This value is applied to all products (i.e. same minimum and/or maximum quantity for each item).
Per item quantity on per product basis – similar to “Per item quantity”, but lets you set different minimum and/or maximum quantity for every product. Works with variable products (i.e. different quantities can be set for each variation).
Fixed quantities per product: You can allow / disallow specific quantity/quantities for a specific product, or all products at once.
Fixed quantity on cart level: Regardless of what products are in cart, you can set specific quantity/quantities that are only allowed in cart.
Specify min / max / fixed quantities per category: This can let you specify total number as min/max/fixed for all products under the same category.
Product Quantity for WooCommerce plugin also includes these features:
Enabling decimal quantities in WooCommerce,
Replacing standard WooCommerce quantity number input with dropdown,
Setting exact (i.e. fixed) allowed or disallowed quantities (as comma separated list),
Validating and (optionally) correcting quantities on add to cart button click,
Forcing initial quantity on single product page and/or archives to either min or max quantity,
Setting quantity input style,
Customizing messages your customer sees,
Enabling/disabling cart notices,
Optionally stopping customer from reaching the checkout page on wrong quantities,
Adding product quantity info on single product and/or archive pages.