McDonald was given a discount for his guilty plea and co-operation with stewards.
But McDonald's lawyer Bret Walker has argued a six-to-nine month suspension would be more appropriate considering 25-year-old McDonald's "extreme youth".
If his ban is reduced to a suspension, McDonald's legal team said the top jockey would volunteer to help with apprentice schools around the state to educate younger jockeys.
However, Racing NSW chief steward Marc Van Gestel hinted McDonald could be considered fortunate to receive the six-month reduction because the special circumstance rule in question states the person must plead guilty as well as co-operate with stewards during the investigation.
Van Gestel said McDonald repeatedly denied having an interest in the bet before an admission of guilt in an interview with stewards in November last year.
When quizzed about the bet in the initial interview with stewards, Van Gestel read a transcript whereby McDonald's comments included:
"You can go through my whole phone, I've done nothing wrong. I don't bet. It would just be like any joe blow in the street coming up to me and saying what's your best today."
He was then quizzed on whether he knew who Gardiner bet with and how much.
"No, I don't want to know, I have a hard enough job as it is."
According to the transcript, McDonald also repeatedly denied being handed any cash from Gardiner or having any transactions between the professional punter and his family.
McDonald later altered his story in the same interview and conceded he had an interest in a bet on Astern in the day of question.
Van Gestel said McDonald was given the reduction because stewards would have had to conduct further investigation work to make the charge stick without McDonald's admission of guilt.
Walker also argued the lack of differentiation in the rule McDonald was charged under between betting on your own mount and on an opposing mount in the race was "very dangerous".
"The best way to proceed is ask the common sense question ... does it make any difference if the breach in question threatens a greater danger to public interest that the rules are designed to achieve or a smaller danger," Walker argued.
"It doesn't mean all conduct committed under that offence should be treated as the same.
"That is very dangerous (to) sentence even the most blameworthy person the same as you would the least blameworthy person.
"The (stewards) saw no difference in a $20 bet than a $20,000 bet.
"The difference between a silly prank to put a $100 (bet) on for me and a plan, let's get together and make sure we have $100,000 (on the horse).
"Not to see the difference would be a (disservice) to public interest."
The inquiry had been adjourned with the appeals panel likely to deliver their verdict later this week.
