英语里面的逗号~

问题描述:

英语里面的逗号~
Source text:Fifteen minutes passed and then ,at five to twelve,the clock stopped.
Translate this sentence into chinese is “15分钟过去了,就在11点55的时候,钟停了.”
My question is why is there a camma between 'then' and 'at'?

我觉得at five to twelve作为插入语对句子补充说明,所以用逗号隔开.