heres a step and drag. you take a step with your front foot and you drag up your back foot.
https://i.ibb.co/xS9777bs/duran-step-drag.gif
the best time to throw a good jab is when he is on his step part of his step and drag.
https://i.ibb.co/hFsm7DmS/dokes-up-jab.gif
thats because his feet aren't under him. but when he has his feet back under him: do you throw your good jab, or do you throw a short jab?