His binary representation is fine, apart from the fact that his least significant bit is on the left rather than the right.
Code:
1 2 4 8
1 0 0 0 = 1
0 1 1 0 = 6
1 0 1 0 = 5
1 0 0 0 = 1
Another little oddity is that when the "4" LED is on, there is some stray light which partly illuminates the "8" LED at the right hand side.
Odd? yes I have to agree, however he has made something and it is working.
A pleasant change from the flood of "gimme circuit for my project I am designing" type posts which we have seen here lately.
JimB