It's a scheme that in English counts accents or stresses per line and then arranges them in a pattern.

这种体系里的英文诗每行都有重读,然后将他们按一定模式排列。

耶鲁公开课 - 现代诗歌课程节选

We have the convention of music of writing this symbol indicating the beat-carrying unit of four so I'm writing a four underneath each of these.

我们有一个约定俗成的书写格式,来表示四拍一单元,所以我在每行这里的下面写上一个四

耶鲁公开课 - 聆听音乐课程节选