I assume you mean a superfecta wheel. Not box. If you are saying that you want to bet one horse (the six) to win with the rest of the field you would calculate like the following.
For nine horse field.
1 horse for WIN
8 horses for PLace (9 less the winner)
7 horses for Show (9 less winner and place horse)
6 horses for Fourth (9 less win,place,show horses)
So a $1 super wheel 1 over all/all/all would be calculated
($1 dollar only get's half the payout)
1*8*7*6 or $336
10 horse
1 * 9 * 8 * 7 = $504
11 horse
1*10*9*8 = $720
12 horse
1 * 11*10*9 = $990