If you notice, if you mirror the boxes across the green "line" the numbers are all the same. Meaning that 1 is a possible answer as well.

soooo....

Case 1 = 9
1+2=3
2+4=6
3+6=9

Case 2 = 3
1
2>4>2
3>6>3>6>3

Case 3 = 1

2<>2
3<>3
4
6<>6
1<>1

So that means that only 4/7 are unaccounted for. Can anyone come up with reasons for why those numbers would be valid as well?