Just a quick heads up, if planning on buying a UCC cert (totally overpriced!) that claims 10 domains - you actually only getten FQDNs total - use them wisely. Consider this example, only covering five domains:
a.com www.a.com b.com www.b.com c.com www.c.com d.com www.d.com e.com www.e.comThis is why we use things like CloudFlare and Let's Encrypt. Depending on your needs. It's 2017, who actually needs to buy SSL certs anymore?
Before my customer purchased the certificate I had to ask, since "domain" means something different to me (you know, an actual domain) and this is what support told me - I verified this after the fact. Now as she states "the primary covers both [www and non-www]" - you can squeeze in an 11th host, but since I needed the domains fully covered, I could only use it for five domains either way.