Hello,

As you know the Theme follows the default WooCommerce mechanism in this regard. The Theme directly doesn’t influence it, the way they work at default WooCommerce level, it is followed at the Theme level too. Regarding knowing on which basis they picks up the Product, please read out the following WooCommerce guide: https://woocommerce.com/document/related-products-up-sells-and-cross-sells/#section-3

Hope this helps !

Best Regards.