You might suppose, the LED Digital Display also can display numbers see Diode Section. You've right!
This Project will display either 3 or 8 when you press the Key depending upon the setting of the Select Switch.
By changing the wiring connections on the Display, you can also make the numbers 1, 6, 2, 7, 4, 9, 5 and 0 appear.
Be sure to keep notes of what you discover.