What kind of adapter was supplied? Because it sounds wrong.

According to the manufacturer's technical data, the double hotplate has a maximum total output of 3,400W.
3,400W is 15A, roughly.

Take a look at the diagram at the bottom of the following page to get started: https://confdg.atlassian.net/wiki....

Type 12 and 13 sockets are approved for a maximum of 10A. In addition, there are usually more than one socket on a fuse which, depending on the age of the installation, is 6, 10 or 13A.
https://www.esti.admin.ch/inhalte...