ABCDEFG = 3211000
As you said, A counts the number of zeroes, and there are 3 zeroes (E, F, G), so A = 3.
B counts the number of ones, and there are 2 ones (C, D), so B = 2.
C counts the number of twos, and there is 1 two (B), so C = 1.
D counts the number of threes, and there is 1 three (A), so D = 1.
There is no four, five, six in, so E, F, G are all zeroes.
That's my opinion