could anyone give me another example please?! I ain't get the quastion :(

The display skips the digit 4 in every position. Assume the display is counting from 1 to 20, this is what we see:

The first number is the actual number, the second is the number that the display will show. Given the second number you should compute the first.

 1: 1
 2: 2
 3: 3
 4: 5
 5: 6
 6: 7
 7: 8
 8: 9
 9: 10
10: 11
11: 12
12: 13
13: 15
14: 16
15: 17
16: 18
17: 19
18: 20
19: 21
20: 22