The amount required for making an order is different for the market and limit/stop orders:
Market order
Exchange sum =
Number of tokens * Price + Exchange Fee + Price change correction*
Limit/stop order
Exchange sum =
Number of tokens * Price + Exchange Fee
Price change correction is 0.2% of the trade's volume. In case the price hasn't changed or changed towards a better value, this sum won't be charged or a part will be returned to your account balance.