In this case, you can consider the fact "How you have configured your website". To determine this, you can browse your website for a while and check the web address(URL) of a website, whether it stays on with WWW or without the WWW in front of the domain.
If the address stays with WWW, your website is configured to work with WWW, and SSL should be purchased with WWW. On the other hand, if the address stays without WWW, you should order the SSL without WWW.
