Hello,
Additional information tab and product attributes are handled by WooCommerce template files and can’t be changed in our theme scope. To change this view you may need to customize WooCommerce template files. The file the contain this code is located in woocommerce/templates/single-product/product-attributes.php
Here is a code line that displays all attribute’s values separated by comma
echo apply_filters( 'woocommerce_attribute', wpautop( wptexturize( implode( ', ', $values ) ) ), $attribute, $values );
Regards