With xLights 3, most of the effects had a speed slider. It was a pain to adjust the slider so that the effect would cycle exactly to the timing mark. Think of garlands filling a tree exactly to the 4 beats. You had to adjust the speed, play the song, adjust again, and again until it was 'close enough'
With xLights4, most effects cycle once or more to the width (timespan) of the timing mark. When Gil said make the effect bigger, he means make the effect stretch a longer amount of time. You can use layers to start another effect on the same model before the first effect completes a cycle of whatever it is cycling (bars, curtain, garlands, etc.)