The 7-segment displays in that circuit are actually controlled by eleven wires. 7 are used to light up the required segments, and 4 are used to select each display. The Microcontroller will switch through each of these displays in turn, outputting the required digit via the 7 data lines. It does this so quickly, that your eyes see the entire display lit up at the same time.
There'll be a display function within the software for the Microcontroller which controls the multiplexing and update of the displays.
Brian