什么是"ASK-Certification of successfully completed university

请各位兄弟姐妹帮忙了,要申请德国大学MASTER,他们要提供下面这个东西,看了网站稀里糊涂的,不知道他们到底要什么,要怎么申请,是否要参见什么测试?请各位指点下,多谢了!

If we are persuaded that you can follow the Programme you can apply for it.
> As you hold a University Degree from outside of Germany, make sure that
> you send us the "ASK-Certification of successfully completed university
> degree for admission to Graduate Studies" of the Ausländerstudienkolleg
> Konstanz (www.ask.htwg-konstanz.de).