There are two types of trading commissions on HitBTC: fees (0.1%) and rebates (0.01%).
Fees are those that you pay, and rebates are being paid to you.
The logic is as follows: you're paying for emptying the order book, and you're being paid for adding new lines in the order book.
For example, you're creating a market order. Being executed, it removes liquidity from HitBTC order book, fills other users' orders. Same thing happens when you're creating limit order which already has suitable pair in the order book. In that case you're paying 0.1% fee as your order is being executed.
In case you're creating a buy limit order below the current price, or a sell order above the current price, your order is being added to the order book. You're increasing the liquidity, that's why you're being paid with 0.01% rebate as your order is being executed.
Take a look at the picture. Fee and rebate are displayed right above the "Sell/Buy" button. And don't forget to learn more about how fees are calculated.