Amount of commissions depends on what type of account you want to open.

If you will chose Classic account, then you will not have any commissions. Broker created commission-free conditions for this type of account.

If you will chose ECN account, then you will have some commissions. Broker set commissions of $4.5 per lot round-turn.
If explain it in simple words, then if you trade a 1.00 lot, your commission will be $4.5
And if you trade, for example, 0.01 lots, commission will be $0.04
As you can see, when trading the smallest lot, commission is only 4 cents.

There are two options, whether you trade with spreads or commissions. In this regard, broker offers two account types Classic and ECN ones, speaking of the first one spreads are floating from 1.7 pips, sometimes lower, sometimes higher, as for the second option - commissions equate to $4.5 per lot round-turn, meaning that if you trade standard 0.01 lot size, for opening/closing a trade, you will charged with less than 0.05 cents.