If you're willing to buy 300 shares at 60, but only 100 shares at $100 you can enter two bids:
100 shares at $100
200 shares at $60
This will satisfy your demand position.
100 shares at $100
200 shares at $60
This will satisfy your demand position.
I would still enter two bids; it's just a matter of adjusting how many at each level.
All the shares in the auction are sold at the same price. If the market clears at 60, a person entering the bids I described would buy 300 shares at 60.