The facet type "conjunctive" allows filters using the logical AND operator between refinements.
If you'd like to allow users to select multiple facet values with a logical OR operator, you should select "disjunctive" as the facet type. You can hover over the facet and click 'edit' to change the facet type.
For more information about Faceting configuration on our Shopify plugin, you can review this documentation. You can also learn more about conjunctive and disjunctive faceting in this guide.