How inheritance works
Rules are resolved per field, not per product. For each of min, max, step and default the most specific value wins:
variation → product → role (Pro) → category (Pro) → store default
A blank field means inherit. So a product with only min = 4 filled keeps the store’s step and maximum.
Setting a product rule
Edit the product and open the Quantity & Pricing tab.
Tick Enable quantity rule for this item.
Fill only the fields you want to override. 0 in min or max means “no limit” (different from blank, which means “inherit”).
Quantity input mode — Free number field (default) or Only specific values (dropdown) (Pro) with Allowed values such as 12, 24, 48.
Update the product.
Variations
Each variation has the same fields inside its own panel. Leave them blank to inherit the parent product’s rule. On the front end the field, its limits and the hint switch the moment a variation is selected.
Stock
The effective maximum is always the lower of your rule and the available stock. If stock drops below the minimum, the product shows the “stock below minimum” message instead of a broken field.
Sold individually
WooCommerce’s Sold individually flag normally forces quantity 1. When a rule needs a real quantity field the plugin overrides the flag; use the qmtp_override_sold_individually filter to keep WooCommerce’s behaviour.