That total was made up of $262,000 in consequential loss reparation because of Malthus' inability to work, $110,000 for emotional harm damage, $30,000 in fines and $3000 in court costs.
McKee, who had 31 years' experience in the industry, pleaded guilty to one charge of exposing a person to risk of serious harm or death after a WorkSafe NZ investigation.
But a few months later, he appealed the sum, claiming it was "manifestly excessive" as the consequential loss reparation - $262,000 - was incorrectly calculated.
In July 2016, Malthus was hired to work as a stable hand, with ambitions to become a jockey.
She had a small amount of horse-riding experience but had never ridden a thoroughbred working racehorse before the day of the accident.
McKee had never seen Malthus ride but allowed her into the saddle of a 3-year-old thoroughbred.
Wearing a helmet, vest and riding boots and accompanied by an apprentice jockey on another horse, Malthus rode out onto the training track and completed the first lap at a trot.
Malthus then took the horse on a second lap at a canter but lost control.
"Unfortunately this led to panic," Judge Sainsbury earlier said. "An inexperienced rider reacting to the horse only made things worse."
Sophia Malthus was left with almost no sensation or motor skills from the collarbone down. Photo / File
Those around the track attempted to shut the gates to keep the horse from bolting, but the animal gained speed and headed straight for the perimeter fence.
"It appears she hit the fence, Judge Sainsbury said. "Alternatively, she may have been struck by one of the horse's hooves."
Malthus broke the C5 vertebrae in her spine and has been left with almost no sensation or motor skills from the collarbone down.
She now requires constant care while living with her parents and has been told she will never walk again.
At the time of the accident, Malthus worked, on average, 37 hours a week.
In a recently released High Court decision, Justice Grant Powell judged that Malthus' earnings at the time of the accident had in fact been miscalculated.
Powell said that the issue lay in the fact that in the earlier judgement, Judge Sainsbury had rounded up Malthus' hours to 40 per week, an approach taken under ACC legislation.
"While Judge Sainsbury's conclusion is readily understood in terms of the dreadful injury suffered by Ms Malthus and the obvious effect that this will have on the future earning capacity for one so young, it does not satisfactorily explain why the loss suffered by Ms Malthus is ostensibly able to be increased with reference to the calculation of weekly compensation under the Accident Compensation Act ..."
Stephen McKee, centre, outside the Auckland District Court last August next to his lawyer Paul Wicks QC and behind the WorkSafe prosecutors. Photo / Alex Burton
But the calculation of Malthus' consequential loss, by definition, must be done by her actual earnings based on her hours of work pre-injury, Powell said.
"The fact that the Accident Compensation Act formula means she is entitled to a greater level of compensation relative to her actual earnings cannot change the level of those actual earnings at the time of the accident," he said.
Justice Powell said Malthus' actual earnings should be based on the 37 hours per week she was working.
This meant her reparation had to be cut by just over $106,000 to $156,000.
McKee also appealed the reparation payment, saying it should have taken into account the lump sum the ACC paid.
But Powell said it was clear that the lump sum Malthus received "was in respect of her injury and was entirely unconnected to any reparation for consequential loss in relation to earnings".
