KuCoin uses a taker - maker fee model for determining its trading fees. Orders that provide liquidity ("maker orders") are charged different fees than orders that take liquidity ("taker orders").
When you place an order and it is executed immediately, you are considered as a Taker and will pay a fee of 0.10%.
When you place an order which is not immediately matched to enter a buy or sell order, and you are considered as a Maker and will pay a fee of 0.10%.
When you place an order that gets partially matched immediately, you pay a Taker fee for that portion. The remainder of the order is placed to enter a buy or sell order and, when matched, it is considered as a Maker order, and the Maker fee will then be charged.