PredictIt deducts only the amount necessary to cover a trader’s potential losses (“risk”) in both single-contract and multiple-contract markets. In a single-contract market, the calculation of risk is equal to the amount you paid for your shares.
In markets with multiple contracts, the calculation of risk is more complicated, but the principle is the same. There is no reason for us to deduct more from a trader than he or she could possibly lose.
For more details on multiple-contract markets, see How to Trade on PredictIt.