Regarding the first move, 3 bits store 8 values. However, the spare value on move 3 signals us to ignore any value in the original move 3 bits and treat it as a

Regarding the first move, 3 bits store 8 values. However, the spare value on move 3 signals us to ignore any value in the original move 3 bits and treat it as a special case to give the 9th value we need.