Minnell was flown to Wellington Hospital in critical condition but survived.
At April's sentencing Pollard also received a concurrent sentence of nine months' imprisonment for failing to stop.
This was reduced by the Court of Appeal to six months.
Pollard's lawyer, Peter Brosnahan, argued the prison sentences were "manifestly excessive" for a range of reasons.
But the one the court agreed with was that the starting point, when calculating the final sentence, was too high because it took into account increases for the failing to stop charge and previous convictions.
Brosnahan said the charge itself encapsulated Pollard's culpability and there were no aggravating factors other than the inherent danger in heavily accelerating while driving through a crowd of people on a road.
The Crown argued there was no error in considering the failure to stop conviction separately and "the judge was entitled to impose an additional uplift on account of earlier offending".
But the Court of Appeal ruled additional sentence imposed considering those two matters "was excessive".