have a big supper与 have supper？

supper本身是不可数的,而且have supper是固定用法,就是吃晚饭.但是中间有形容词Big修饰时往往指具体的一餐饭,所以用a来修饰.,2,have a big supper与 have supper
为什么前一个加A,后一个不加

扩展阅读：around the world ... think highly of sb ... admire the moon ... learn by doing ... read a poem ... what s more ... is for family ... think little of ... have fun ...