Accepted duty rows are checked against an output-voltage ceiling. Exact arithmetic here means exact results for the stated model inputs; measured inputs still carry uncertainty and significant-figure limits.
highlighted = computed this step
1/3 duty row
Input stays 12 V. Accepted duty 1/3 gives output 4 V against a 6 V ceiling, so margin is 2 V.
Vo=4V,m=2V⇒pass
1/2 duty row
Input stays 12 V. Accepted duty 1/2 gives output 6 V against a 6 V ceiling, so margin is 0 V.
Vo=6V,m=0V⇒pass
2/3 duty row
Input stays 12 V. Accepted duty 2/3 gives output 8 V against a 6 V ceiling, so margin is negative 2 V.