Unlike market orders, limit orders will not automatically fill once your desired price has been reached. Limit orders are two-sided, meaning that the order will need to be filled by another user. This means that there is no guaranteed or specific timeframe for when your order will be filled.
For example, if you set a limit order to sell XCM at 0.601, another user would need to place a limit order to buy XCM at 0.601 for your order to fill. However, please note that if other users have placed a limit order at the exact same price as you, then you would be in a queue and whoever set up their order first would therefore have their order filled first.
Another way that your limit order can be filled is if your sell order is at the top of the order book (next to be filled), and another user then placed a market buy order for the same asset, their marker order would fill your limit order.
If you are looking for your order to fill instantly, then you would need to place a market order.