In the MT4 Instant Execution account type order window, you can choose to set a maximum deviation pip-range for your orders that is acceptable to you in the event that your order cannot be filled at the requested price. In other words, checking the maximum deviation box and setting it to two pips indicates that you are willing to accept a price that deviates 2 pips above or below the requested price. This will reduce the number of requoted orders, which is especially helpful at times of high market volatility. When the maximum deviation box is left unchecked, your order will only be executed if it is available at the exact price you requested. Otherwise, the order will be requoted. This applies only to 'Instant Execution'.