Schritte A11 Audio High - Quality

At first glance, this seems confusing. The standard series usually goes from A1 to B1. So, what on earth is "A11"?

: Channels often provide lesson-by-lesson walkthroughs with audio, such as the Schritte Plus Neu A1.1 playlist . Schritte international Neu - Hueber Verlag schritte a11 audio