I just looked it up. It is a sentence in my graduation diploma (Abiturzeugnis):

Dieses Zeugnis schließt den Nachweis des Latinums gemäß der Vereinbarung über das Latinum und das Graecum (Beschluss der Kultusministerkonferenz vom 22. September 2005 in der jeweils geltenden Fassung) ein.

This diploma includes the certificate of the Latinum according to the agreement about the Latinum and Graecum (Decision of the conference of ministers of education of september 22^nd 2005 in the version currently in force).

The Graecum is the same as the Latinum but for ancient greek.