If the domain owner has sub-server creation privileges, you may limit the number of non-alias servers that can be created here. Note that this limit cannot be effectively higher than the Default limit on number of virtual servers, as the overall limit on virtual servers applies to both alias and non-alias domains. A limit of `0` prevents the creation of non-alias servers completely.

This is useful if you want to allow a domain owner to create an unlimited or higher number of alias servers, but limit the more expensive sub-servers he can create.