The wildcard SSL certificates issued by ServerTastic cover both *.yourdomain.com and yourdomain.com
For example. If you ordered a wildcard SSL for *.servertastic.com it would also secure servertastic.com
However if you ordered a wildcard SSL for *.server1.servertastic.com it would only cover sub-domains of server1.servertastic.com. It would not cover servertastic.com.
If you want to secure *.sub.yourdomain.com and sub.yourdomain.com then you will need to purchase multiple certificates.
Also not it is not possible to order a wildcard certificate to secure *.*.yourdomain.com