You can adjust the entry delay time on the panel by going to settings > Advanced Settings (Default installer code is 1111) > Installation > Security and Arming
Typically motion detectors are programmed so that they won’t go off as long as the entry delay has been started. If the door you entered in doesn’t have a sensor on it or the sensor is bypassed then the motion detector will cause the system to go off immediately. I believe setting the motion detector’s sensor group to 20 will give it an entry delay