How does the app decide which size chart a product shows?

The matching order is:

1. Exact product assignment — a chart assigned directly to that product.
2. Collection assignment — a chart assigned to a collection the product belongs to. If more than one assigned collection matches, the collection higher in your list wins.
3. Automatic rule (Pro) — the first enabled rule that matches the product, in your rule order.
4. Everything else — the store-wide chart selected for products that matched nothing above.

If none of these levels matches, the block renders nothing at all. It does not leave an empty heading, wrapper, or placeholder on the page.
To check a specific product on Pro:

1. Open Simulator.
2. Select the product.
3. Review the chart that will be shown and every matching level the app checked.

The simulator uses the same matching order and the currently published data as the storefront.