1 if there is a complete circle, or 0 if there is no circle.

For example, 6, 9 and 0 have a circle, all of which are 1.

8 has two circles, so it is 2.

1, 2, 3, 4, 5 and 7 all count as 0.

If I am not mistaken, it should be like this.

5555 is 0.

0000 is1+1+1+1= 4.