How do I index the EAN?

Hi, I have installed this EAN for WooCommerce plugin ( https://www.ads-software.com/plugins/ean-for-woocommerce/ ) and I would like to know what is the proper way to index the EAN codes. So far I had had the “some” setting with just the “_sku” value. Should I use “ean”, “_ean”, or something else? I have kept the “_sku” value, so I am separating them with commas. Thank you.