Move the minute hand. The board shows the time the way it is written in Berlin, and the line below shows what somebody would actually say to you.
Drag the yellow knob around the dial. Yellow marks are where German jumps to the next hour.
Written German time is a 24-hour clock. A door that says bis 18 Uhr closes at 6 pm, and a ticket for 20:15 is a quarter past eight in the evening. Spoken German switches back to twelve, which is where halb starts costing people an hour.