Please bear in mind:
As hostname you can specify the corresponding subdomain (e.g. "www") or the following 2 wildcards:
* - stands for all subdomains of the domain (www.domain.de / subdomain.domain.de)
@ - stands for the actual domain (wildcard entry) (domain.de)
Please note that the TTL has to amount to at least 60. Lesser values aren't accepted by the system.