When you choose multiple runners for each race, you are effectively placing multiple single bets (otherwise known as combos). The payout formula for Hourly Quaddie is your stake per combo multiplied by the product of the 4 winning runner starting prices. In the event where short priced favourites are winning races, it is possible that the Quaddie payout price is less than the total amount staked.
For example, In a scenario where a punter chooses 3 runners (including the favourite) in reach of the 4 races, they will have placed an 81 combo bet (3x3x3x3). If they staked $81 on the Hourly Quaddie bet, at $1 per combo, they would receive $1 x the Quaddie price.
If the winning runners are all favourites paying $2 - the Quaddie payout would be $16 ($2x$2x$2x$2).
This scenario also occurs in traditional Tote Pool based Quaddies.